feat: add flowspec doctor and GPG signing

docs/guides/gpg-signing.md

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+# Agent GPG Commit Signing
+
+This guide covers GPG commit signing for Flowspec agents, enabling cryptographic verification of agent-generated commits.
+
+## Overview
+
+Flowspec agents can generate their own GPG keys and sign commits to provide:
+- **Cryptographic verification** of agent authorship
+- **Non-repudiation** - proof that commits came from the agent
+- **Trust chains** - link agent commits to their originating workflow
+- **Audit trails** - track which agent made which changes
+
+## Quick Start
+
+### 1. Set Up GPG Signing
+
+```bash
+# Generate agent GPG key and configure git
+flowspec gpg setup
+
+# Output:
+# ✓ GPG key generated
+# ✓ Git configured for signing
+#
+# Fingerprint: A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0
+```
+
+### 2. Verify Status
+
+```bash
+# Check GPG signing status
+flowspec gpg status
+
+# Output:
+# ┌─ Agent GPG Signing Status ─┐
+# │ Status          Configured  │
+# │ Fingerprint     A1B2C3...   │
+# │ Git Signing     Enabled     │
+# └─────────────────────────────┘
+```
+
+### 3. Make Signed Commits
+
+Once configured, all commits in the repository will be automatically signed by the agent:
+
+```bash
+git commit -m "feat: add new feature"
+# Commit is automatically signed with agent's GPG key
+```
+
+## Commands
+
+### `flowspec gpg setup`
+
+Generate a new GPG key and configure git for commit signing.
+
+```bash
+# Set up in current repository
+flowspec gpg setup
+
+# Set up in specific repository
+flowspec gpg setup --project-root /path/to/repo
+
+# Force key regeneration
+flowspec gpg setup --force
+```
+
+**What it does:**
+1. Generates a 4096-bit RSA GPG key for "Flowspec Agent <agent@flowspec.local>"
+2. Stores the key fingerprint in the system keyring
+3. Configures local git settings:
+   - `user.signingkey`: agent's GPG fingerprint
+   - `commit.gpgsign`: true
+
+### `flowspec gpg status`
+
+Show current GPG signing configuration and status.
+
+```bash
+# Check status in current repository
+flowspec gpg status
+
+# Check status with detailed key information
+flowspec gpg status --verbose
+
+# Check status in specific repository
+flowspec gpg status --project-root /path/to/repo
+```
+
+**Output includes:**
+- Configuration status (configured/not configured)
+- GPG key fingerprint
+- Git signing status (enabled/disabled)
+- Key creation date (with `--verbose`)
+- Key identity (with `--verbose`)
+
+### `flowspec gpg rotate`
+
+Rotate the agent's GPG key (delete old key, generate new key).
+
+```bash
+# Rotate key (with confirmation prompt)
+flowspec gpg rotate
+
+# Rotate key without confirmation
+flowspec gpg rotate --yes
+
+# Rotate key for specific repository
+flowspec gpg rotate --project-root /path/to/repo
+```
+
+**When to rotate:**
+- Regular security practice (e.g., annually)
+- Key compromise or suspected compromise
+- Agent role change or re-provisioning
+- Compliance requirements
+
+**Warning:** Rotating a key does not re-sign historical commits. Old commits will still reference the old key fingerprint.
+
+## Key Management
+
+### Key Storage
+
+- **GPG Keychain**: Keys are stored in the user's GPG keychain (`~/.gnupg/`)
+- **Fingerprint**: The key fingerprint is stored in the system keyring for quick retrieval
+- **Service Name**: `flowspec-agent-gpg`
+- **Username**: `agent-key-fingerprint`
+
+### Key Properties
+
+```
+Name:       Flowspec Agent
+Email:      agent@flowspec.local
+Type:       RSA
+Length:     4096 bits
+Expiration: None (does not expire)
+```
+
+### Security Considerations
+
+1. **No Passphrase**: Agent keys are generated without a passphrase for automated signing
+2. **Local Storage**: Keys are stored locally on the agent's system
+3. **Per-User**: Each user account has its own agent key
+4. **Repository Config**: Git signing is configured per-repository (local config)
+
+## Git Configuration
+
+GPG signing modifies local git configuration:
+
+```bash
+# View current configuration
+git config --local user.signingkey
+git config --local commit.gpgsign
+
+# Manual configuration (not recommended - use 'flowspec gpg setup')
+git config --local user.signingkey A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0
+git config --local commit.gpgsign true
+```
+
+## Checking GPG Status
+
+Use the GPG-specific commands to inspect signing configuration:
+
+```bash
+# Check GPG signing status
+flowspec gpg status
+
+# Check with detailed key information
+flowspec gpg status --verbose
+```
+
+## Verifying Signed Commits
+
+### On GitHub
+
+GitHub automatically verifies GPG-signed commits if the public key is uploaded:
+
+1. Export the agent's public key using the exact fingerprint from `flowspec gpg status`:
+   ```bash
+   # Replace with the fingerprint shown by `flowspec gpg status`
+   gpg --armor --export A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0 > agent-key.asc
+   ```
+
+2. Add the key to GitHub:
+   - Go to Settings → SSH and GPG keys → New GPG key
+   - Paste the contents of `agent-key.asc`
+
+3. Signed commits will show a "Verified" badge
+
+### Locally
+
+```bash
+# Verify a signed commit
+git log --show-signature -1
+
+# Output:
+# commit abc123def456...
+# gpg: Signature made Thu Apr  3 12:34:56 2025 UTC
+# gpg:                using RSA key A1B2C3D4E5F6A7B8C9D0...
+# gpg: Good signature from "Flowspec Agent <agent@flowspec.local>"
+```
+
+## Key Rotation Workflow
+
+Key rotation is important for security best practices:
+
+```bash
+# 1. Rotate the key
+flowspec gpg rotate --yes
+
+# Output:
+# Old fingerprint: A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0
+# New fingerprint: F0E9D8C7B6A5F4E3D2C1B0A9F8E7D6C5B4A3F2E1
+
+# 2. Export new public key (use the new fingerprint from the output above)
+gpg --armor --export F0E9D8C7B6A5F4E3D2C1B0A9F8E7D6C5B4A3F2E1 > agent-key-new.asc
+
+# 3. Update GitHub/GitLab with new key
+
+# 4. (Optional) Sign a rotation commit
+git commit --allow-empty -m "chore: rotate agent GPG key
+
+Previous key: A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0
+New key:      F0E9D8C7B6A5F4E3D2C1B0A9F8E7D6C5B4A3F2E1
+
+Signed-off-by: Flowspec Agent <agent@flowspec.local>"
+```
+
+### Rotation Schedule Recommendations
+
+| Environment | Rotation Frequency | Rationale |
+|-------------|-------------------|-----------|
+| Development | Annually | Low risk, convenience |
+| Staging | Quarterly | Moderate risk |
+| Production | Monthly | High security requirements |
+| Compromised | Immediately | Security incident |
+
+## Troubleshooting
+
+### GPG Not Found
+
+```
+Error: GPG not found. Please install gnupg.
+```
+
+**Solution:** Install GPG:
+```bash
+# Ubuntu/Debian
+sudo apt install gnupg
+
+# macOS
+brew install gnupg
+
+# Fedora/RHEL
+sudo dnf install gnupg
+```
+
+### Git Not a Repository
+
+```
+Error: Not a git repository: /path/to/dir
+```
+
+**Solution:** Run `flowspec gpg setup` inside a git repository or specify `--project-root`:
+```bash
+cd /path/to/repo
+flowspec gpg setup
+```
+
+### Commits Not Signed
+
+**Symptoms:** Commits don't show "Verified" badge
+
+**Diagnosis:**
+```bash
+# Check git config
+git config --local commit.gpgsign
+# Should output: true
+
+git config --local user.signingkey
+# Should output: your fingerprint
+
+# Check GPG key exists
+gpg --list-keys agent@flowspec.local
+```
+
+**Solution:**
+```bash
+# Reconfigure signing
+flowspec gpg setup
+```
+
+### Keyring Access Error
+
+```
+Error: Failed to store fingerprint in keyring: ...
+```
+
+**Solution:** Ensure the system keyring is accessible. On Linux, you may need to install and configure a keyring backend:
+```bash
+sudo apt install gnome-keyring  # Ubuntu/Debian
+# or
+sudo dnf install gnome-keyring  # Fedora/RHEL
+```
+
+## Advanced Usage
+
+### Multiple Repositories
+
+Each repository requires its own `flowspec gpg setup` to enable signing. The same agent key is used across all repositories:
+
+```bash
+# Repository A
+cd /path/to/repo-a
+flowspec gpg setup
+
+# Repository B
+cd /path/to/repo-b
+flowspec gpg setup
+
+# Both repos use the same agent key, but each has local git config
+```
+
+### Disable Signing for a Repository
+
+```bash
+# Disable automatic signing
+git config --local commit.gpgsign false
+
+# Or unset the config
+git config --local --unset commit.gpgsign
+git config --local --unset user.signingkey
+```
+
+### Export Public Key for Distribution
+
+```bash
+# First, get the exact fingerprint from flowspec
+flowspec gpg status
+
+# Use the specific fingerprint in export commands
+# Replace A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0 with your actual fingerprint
+
+# Export ASCII-armored public key
+gpg --armor --export A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0 > agent-public-key.asc
+
+# Export binary public key
+gpg --export A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0 > agent-public-key.gpg
+
+# Show fingerprint details
+gpg --fingerprint A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0
+```
+
+### Manual Key Deletion
+
+```bash
+# Look up the key fingerprint
+flowspec gpg status
+
+# Delete secret and public key by fingerprint
+gpg --delete-secret-and-public-key A1B2C3D4E5F6A7B8C9D0E1F2A3B4C5D6E7F8A9B0
+
+# Delete fingerprint from keyring
+# (This is handled automatically by 'flowspec gpg rotate')
+```
+
+## Security Best Practices
+
+1. **Regular Rotation**: Rotate agent keys on a schedule appropriate for your security requirements
+2. **Key Backup**: Consider backing up the private key to a secure location (encrypted)
+3. **Audit Logs**: Monitor telemetry for signing activity
+4. **Access Control**: Restrict access to the agent's keyring and GPG directory
+5. **Verification**: Regularly verify that commits are being signed correctly
+6. **Incident Response**: Have a plan for key rotation in case of compromise
+
+## Related Documentation
+
+- [Telemetry Guide](./telemetry-guide.md) - Telemetry integration with GPG fingerprints
+- [Security Workflow](./security-workflow.md) - Security scanning and compliance
+- [Git Hooks](../reference/git-hooks.md) - Custom hooks for commit signing
+
+## References
+
+- [GPG Manual](https://www.gnupg.org/documentation/manuals/gnupg/)
+- [Git Signing Documentation](https://git-scm.com/book/en/v2/Git-Tools-Signing-Your-Work)
+- [GitHub GPG Verification](https://docs.github.com/en/authentication/managing-commit-signature-verification)