STR-02c: working-tree map in runtime

[kaanozhan]

Reverses STR-02b D1. While the tracked .frame/STRUCTURE.json held the working-tree view, it differed from the committed map, and Git refused checkout/switch/pull.

What changes

• Two views. The live working-tree view lives in .frame/runtime/structure/working.json (never committed). The tracked STRUCTURE.json is the committed view plus prose edits, and is the generation prior for the live view (D1, D2). --full, explicit files and --check operate on the live view (D3).
• Untracked maps (no Git, local sharing, before the first commit) keep mirroring the live view (D5).
• Commit side. The hook stages the index-built map and writes the same bytes to disk, so git status stays clean after a commit. A file with unstaged edits is never overwritten. The worker repairs the stale index a pathspec commit leaves behind (D6). --changed is now the same as --staged, so old --changed + git add snippets work; that check-freshness finding is gone (D7).
• Loss-free upgrade. A tracked map that differs from the index only in generated content (compared with the new authoredView) is archived to recovery/ and restored. Hand edits are kept, and check-freshness reports them (D8).
• Readers. find-module, module-hint, check-freshness and frameStore.getStructure read the live view first (D9). AGENTS/REFERENCE/QUICKSTART wording is updated. The STR-02b hook template's hash is added to the upgradable list.

Tests

npm test: 1109 passing. New real-repository tests cover switch/checkout/pull with live untracked and unstaged work, a clean map after a normal commit, pathspec repair, an old snippet, the upgrade (restored or kept), and working-first readers.

Also checked on this repo: structure-lifecycle.js --once restored the tracked map (old bytes archived), and git status is clean for it.

Spec: .frame/specs/str-02c-working-view-in-runtime/