docs: update audit report resolutions and fix stale OBSERVABILITY.md links

[clouatre]

docs: update audit report resolutions and fix stale OBSERVABILITY.md links

• docs/audit/2026-07-05-v0.22.3.md: add Fixed column to summary table with PR links (fix(ci): arm64 binary, rust-cache SHA, and codeql runner (#1270) #1280-fix(exec): use full seq as slot identifier to prevent concurrent overflow collision #1283); replace Fix/Regression gate/PR group blocks with concise Resolution lines for all confirmed findings; correct F04 (CodeQL stays on AMD64; ARM64 JVM incompatible); update subsystem review statuses; replace Regression Strategy with Resolution Summary table
• docs/OBSERVABILITY.md: delete stale duplicate of docs/METRICS.md (renamed in docs: rename docs/OBSERVABILITY.md to docs/METRICS.md (#1264) #1265)
• docs/ARCHITECTURE.md, docs/DESIGN-GUIDE.md, docs/METRICS.md, docs/ROADMAP.md: replace relative ../OBSERVABILITY.md links with absolute URLs; DESIGN-GUIDE.md metrics schema links updated to METRICS.md

[aptu-dev]

Aptu Review

✅ Approve — This PR updates documentation to reflect recent changes, specifically replacing stale relative links to OBSERVABILITY.md with absolute URLs and cleaning up duplicate files. It also updates the audit report resolutions to include PR links and corrects subsystem statuses.

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_{Posted by aptu}

[aptu-dev]

Aptu Review

✅ Approve — Updates audit report documentation to include resolution details and PR links, removes a stale OBSERVABILITY.md duplicate, and replaces relative links with absolute URLs across several docs files.

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_{Posted by aptu}