D59 — OpenCode hooks: generated JS plugin

Context. After D57/D58, kind: hook remained Unsupported on OpenCode: no declarative hooks to register in a file — OpenCode instead loads JS/TS plugins from ~/.config/opencode/plugins/ (auto-loaded, no entry in opencode.json).

Decision. destDir("hook", _, opencode) materializes the files in .opencode/hooks/<nome>/; Apply generates — if the KB event is mappable (PreToolUse→tool.execute.before, PostToolUse→tool.execute.after, SessionStart/Stop on the generic pub/sub bus filtered by event.type, other events → no plugin) — an entire deterministic plugin file cartographer-<nome>.js that runs the materialized script. Per-file ownership, not per-block: unlike D57/D58, the generated file belongs entirely to Cartographer — rewritten in full on update, deleted on prune, no block parsing. Unmappable event → AppliedResult.Warnings, not an error. The matcher (only PreToolUse/PostToolUse) uses a bidirectional case-insensitive substring comparison (a heuristic, not a guaranteed tool-name table). Rationale. One file per hook is consistent with the existing skill/agent scheme and makes prune trivial (os.Remove), discarding a single "router" plugin that would be harder to maintain incrementally. Open question. The substring matcher is a heuristic: a hook with a very specific matcher might not behave identically on the two providers. Details: docs/sync.md §Agents and hooks.