feat(gui): add a Copy Diagnostics button to the About window

[davidbudnick]

Summary

Adds a Copy Diagnostics button to the About window that copies a privacy-filtered, Markdown diagnostics report to the clipboard for pasting into a bug report. It gives enough detail to reproduce environment-specific issues — device connection, capabilities, missing render images, agent/GUI version skew, asset-cache state — without exposing anything that uniquely identifies the user's hardware.

What it collects

• App — GUI + agent versions (with a mismatch flag), IPC protocol versions, OS + version + arch, locale, accessibility / input-hook / launch-at-login / menu-bar state, build profile, config schema + configured-device count.
• Assets — source (app bundle vs user cache), index size, redacted cache path, bundle presence — the signals behind "preview image not loading".
• Devices (per device) — name, kind, firmware codename, connection type, online, battery, capabilities (buttons/pointer/lighting), DPI, model/config key + wpid + model-ids + ext-model, transports, render state (resolved depot vs silhouette), slot.
• Receivers — model name + VID/PID.

Privacy

Model-level only. Serial numbers, unit IDs, and the Bolt receiver UID are excluded by construction — the report structs have no field to hold them, so a future edit can't leak one by forgetting to redact. The home directory is redacted to ~ in the cache path.

Design

• The data shape and Markdown rendering live in openlogi-core (diagnostics.rs) — platform-free and unit-tested.
• A thin GUI adapter (openlogi-gui/src/diagnostics.rs) maps live AppState (device list, agent status, asset resolver) onto it, refining connection type from the device's announced transports.
• The GUI now retains the full AgentStatus and the raw inventory snapshot (previously discarded after each poll) so the report can include agent version, hook state, and transports.
• Clipboard write uses cx.write_to_clipboard(ClipboardItem::new_string(...)); the button confirms with a "Copied!" label for ~2s.

Testing

• 8 unit tests in openlogi-core cover section rendering, version/protocol mismatch flags, empty/offline devices, the no-serial-or-unit-id guarantee, and direct-connection slot rendering.
• Verified end-to-end on real hardware (built and ran the GUI), confirming the report renders correctly against a live device:

### OpenLogi Diagnostics

**App**
- OpenLogi (GUI): v0.6.6 (release)
- Agent: v0.6.6 (connected)
- IPC protocol: GUI 1 / agent 1
- OS: macOS 26.4.1 (arm64)
- Locale: en-CA (UI: follow system)
- Accessibility: granted · Input hook: installed
- Launch at login: no · Menu bar: yes · Update check: on
- Running from: source build (dev)
- Config: schema 2 · 0 configured device(s) · thumbwheel 14

**Assets**
- Source: user cache · Index: loaded (210 models) · User cache: present
- Cache path: ~/.local/share/openlogi/assets · Bundle assets: absent

**Devices (2)**
- Receiver: Logi Bolt Receiver (VID 046d / PID c548)
- MX Master 3S — mouse (codename: MX Master 3S)
  - Connection: Logi Bolt receiver · Online: yes · Battery: 35% (discharging, good)
  - Capabilities: buttons=yes, pointer=yes, lighting=no
  - Model: 0b034 (model-ids: b034/0000/0000, ext-model: 00)
  - Transports: BTLE
  - Render: mx_master_3s · Slot 2
- G513 — keyboard (codename: G513 RGB MECHANICAL GAMING KEYBOARD)
  - Connection: Wired (USB) · Online: yes · Battery: n/a
  - Capabilities: buttons=yes, pointer=no, lighting=yes
  - Model: 5c33c (model-ids: c33c/0000/0000, ext-model: 05)
  - Transports: USB
  - Render: g513 · direct

Screenshots