docs: cleanup README and trim stale content

[BinHsu]

Summary

• README rewrite: replaced product-pitch framing with platform-engineering-as-a-product context. New README accurately presents the 4-repo model (aegis-platform-aws / aegis-core / aegis-core-deploy / aegis-greeter-deploy), per-component descriptions (gateway_go, engine_cpp, frontend_web), image-flow from merge → ECR → aegis-core-deploy → ArgoCD, CI workflow table, and build stack. No emoji, no Rust (no .rs files exist), no shell_tauri/ or test/golden_audio/ (dirs don't exist on disk).

• Dead links fixed: shell_tauri/ and test/golden_audio/ removed from Project Structure (ADR-0008 marks them Phase 4+ placeholders but they do not exist). All remaining internal README links verified against current filesystem.

• Stale content trimmed or flagged:

  • aegis-aws-landing-zone → aegis-platform-aws in ARCHITECTURE.md (§7 cross-repo section, §8, §10 references), CONTRIBUTING.md (cache migration section), ROADMAP.md (one forward-looking "how to close" line — historical log entries left unchanged as records)
  • ARCHITECTURE.md §7 corrected to 4-repo model; added note that K8s manifests live in aegis-core-deploy, not this repo (per ADR-0036)
  • CONTRIBUTING.md: Go SDK version 1.24.12 → 1.24.13 (matches MODULE.bazel)
  • frontend_web/README.md: "Bazel integration deferred to Phase 4" replaced with current state (aspect_rules_js live, tools/scripts/frontend.sh is the entry point)
  • Rust removed from Tech Stack (zero .rs files in repo)
  • ADR-0034 §D2: flagged <!-- docs ahead of code --> — ADR says memory-only token storage (InMemoryWebStorage) but shipped code uses WebStorageStateStore (localStorage), with explicit trade-off comment in auth.ts:124. Needs a follow-up ADR to close formally.
  • docs/runbooks/fork-and-self-deploy.md: added header note that upstream infra repo is now aegis-platform-aws.

Cross-repo links not changed

github.com/BinHsu/aegis-aws-landing-zone/issues/NNN links in ADRs are historical provenance records. Per the ADR non-rewrite policy (ADR-0005 principle), these are left in place. The relevant context note was added to ARCHITECTURE.md §7 instead.

Test plan

• All internal README links resolve to existing files/directories (verified locally)
• docs/adr/ and docs/runbooks/ are valid directory links (GitHub renders as directory listing)
• CI baseline markdown-link-check passes (check-modified-files-only, so only changed .md files are checked)
• No new aegis-aws-landing-zone forward-looking references introduced

🤖 Generated with Claude Code

https://claude.ai/code/session_014AQtyw8bug7HhRFQbtMJqy

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