fix(natives): resolve better-sqlite3 by fresh fs walk, not cached resolver

[pacphi]

Problem

ak sync could end with a false failure even when everything was actually healthy:

✓ natives: …/ruflo/node_modules/agentdb: native installed; …/agentic-flow/node_modules/agentdb: native built…; agentic-qe: native installed
…
✗ still failing: [natives] 1/1 agentdb location(s) on WASM fallback (data-loss writes)

The heal step reported the location native, yet the final convergence proof reported WASM fallback — and a fresh node process confirmed the on-disk state was native and healthy. So the end state was fine; the proof lied.

Root cause

bsq3Root() resolved better-sqlite3 via createRequire().resolve(). Node's resolution cache (Module._pathCache / _realpathCache) is process-wide and goes stale after an in-process npm install reshapes node_modules. During one sync:

1. healNatives() resolves + builds native better-sqlite3 (priming the cache; the tree has a nested agentic-flow/node_modules/agentdb).
2. healAidefence() runs npm install @claude-flow/aidefence into the ruflo tree → dedupes the nested agentdb away.
3. The convergence proof calls bsq3Root() again → gets the cached root pointing at the now-deleted nested path → binding check fails → false WASM.

agentdbLocations() uses plain fs.existsSync and correctly saw the tree shrink 2→1; only the resolver-backed lookup was stale.

Fix

bsq3Root() now walks up the node_modules chain with fs.existsSync on every call — the Node-resolution equivalent, but reading disk fresh, so it's immune to in-process tree mutation (matching how agentdbLocations() already reads).

• Identical behavior for the resolvable / not-resolvable / native / WASM cases (existing tests unchanged).
• Adds coverage for hoisted resolution (the real ruflo/node_modules/agentdb → ruflo/node_modules/better-sqlite3 layout) and the nested→hoisted mid-process move that triggered the bug.

Verification

npm run check green (exit 0): typecheck, eslint, markdownlint, build, 76 kit + 20 statusline tests. Verified live on the reporting machine: ak status shows ✓ natives native better-sqlite3 in 1 agentdb location(s) and ak sync now reports ✓ converged — no failing subsystems.

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