docs: release readiness records, documentation alignment, and benchmark evidence

[rogerdigital]

Summary

Completes B5 and the C0/C4 runnable evidence for the 1.0.0 release readiness plan:

• B5 documentation alignment — README: orphan detection now lists the real reference channels (Markdown links/embeds/frontmatter, Canvas file nodes and group backgrounds) and the incomplete-coverage trash block; duplicate detection describes the two candidate groups and hash verification; the keep policy matches pickAutomaticKeepPath (highest inbound reference count, ties lexicographic; multi-referenced groups require an explicit choice; references never rewritten); external-link severities match the actual classification; settings note that automatic scans and network access stay off by default plus the post-fix synchronization recovery step. docs/cli.md documents comparison semantics version 4. CLAUDE.md is synced with AGENTS.md (it was several versions stale). The old umbrella roadmap links to this plan's delivery status.
• C0 evidence record — docs/validation/1.0.0-readiness.md with automated-gate evidence (S0, A1–A3, B1–B5 with commits, RED/GREEN notes, CI links), blocked native-acceptance entries (no desktop/mobile devices in this session), and environment restoration notes.
• C4 runnable part — CLI benchmarks, same machine, serial, 0.8.1 (fdcc77d) vs candidate: 400/150 total 183ms → 171ms (−6.6%), 10 000/2 000 total 7106ms → 6982ms (−1.7%), within the ≤20% budget. Native UI rows recorded as Blocked.
• Readiness plan progress table updated with actual statuses.

Documentation and records only; no behavior change.

Validation

• npm run lint && npm run lint:obsidian-warnings && npm run build && npm test — 969 tests pass.
• B5 claims verified against reference-index.ts, duplicate-files.ts, and action-policy.ts (logic suites pass; not native acceptance).