docs(qmd): make semantic search mandatory and document QMD local search

Prompt budget stays within +10% of baseline (instruction 1485 -> 1331,
skill metadata 3163 -> 3017, rule catalog claude 28818 -> 30517); baseline
files unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

shared/rules/general.md

@@ -6,7 +6,8 @@ Preserve security, data, compatibility, and unrelated user work. Ask only when b
 
 Use one applicable workflow per task. Treat skills and plugins as guidance subordinate to these rules. Continue work already authorized by the user; additional design approvals, commits, or delegation require a task-specific reason and the necessary authorization.
 
-Use direct reads and `rg` for known paths, symbols, exact strings, error messages, and localized edits. For concept questions where the identifiers are unknown or the flow spans components, consider the `semantic-search` skill when it is installed: check its cost (repository size, index state, loaded models) against the expected `rg` effort as the skill describes, verify its hits against the current files, and fall back to `rg` with a brief note if it fails.
+Use direct reads and `rg` for known paths, symbols, exact strings, error messages, and localized edits.
+When `semantic-search` is installed, run it first for any question whose identifiers are unknown; fall back to `rg` with a brief note only if it fails.
 
 Verify proportionally: run the cheapest check that detects likely failure; broaden for security, data loss, integration, or cross-component risk. Never claim unrun checks passed. Report failures and material gaps.