fix(best-practices): restore canonical content, dedupe, sync script, spec exemplar
- best-practices/v1: replace 9 stale symlinks (into planning/v1) with real files
synced byte-identical from the canonical best-practices project; add INDEX.md,
scripting.md, mechanical-test-generation.md (canonical had drifted heavily,
e.g. api-design.md 463->807 lines)
- planning/v1: delete duplicated best-practices/ copy (requires: inheritance
confirmed via spec/harness.md HC-1/HC-7)
- scripts/sync-best-practices.sh: idempotent re-sync from canonical checkout
- code-methodology/v1: INDEX.md + scripting.md references now resolve; point
test-writing tasks at mechanical-test-generation.md
- spec-writing/v1: worked spec exemplar (module layout table, Why: lines, exact
error messages, parametrize pattern table) + CLAUDE.md pointer + mount entry
dab3db3727