fix: harden greenfield + repair paths (2nd-pass review — 2×P1, 2×P2)

[agjs]

Why

A second-pass review of the greenfield/repair paths (shipped in 0.20.0 via #44) found four real issues — two security/correctness P1s and two P2s. This is the hardening pass before the feature is settled.

Fixes

[P1] Contract persistence trusted model-controlled feature IDs as paths.
writeContract did join(dir, \${feature.id}.md`), and the planner accepted any string id — so with TSFORGE_CONTRACT=1a feature id like../../../README escaped the state dir (reproduced in a temp repo). Now: feature ids are validated kebab-case (isFeatureId) at **both** parse (plan.ts) and load (state.ts), so a path-like id is dropped; writeContractadditionally derives the filename from abasenamewith a safe"feature"` fallback (defence-in-depth).

[P1] Rollback left newly-created binary/asset files behind.
restoreFiles tombstoned through resolveScopeFiles, which intentionally filters out .svg/images/fonts for prompt safety — so a failed repair that created icon.svg reported "reverted" while leaving it on disk (reproduced). Added resolveScopeFilesForRollback (uncapped, ignored-dirs-only, binary-inclusive); the snapshot's existed-set and the tombstone scan use it, while text content is still captured via the filtered resolver (writing back .text() of a binary would corrupt it).

[P2] Greenfield --browser resolved relative paths from the launcher cwd, not --dir.
Normal gate checks run inside --dir, but greenfield's in-process renderCheck did not. Relative --browser is now resolved against args.dir.

[P2] Accept-rate metrics undercounted multi-file reverts.
One reverted event subtracted only 1, but a failed batch may roll back N edits — making /trace optimistic. The reverted event now carries a batch mutation count (review-repair + quality tally edit/create events during the attempt); analyzeEvents subtracts event.count (default 1), and count round-trips through the ledger.

Verification

• bun run validate green — 1421 pass / 0 fail.
• New regression tests for each fix; both P1s flip-and-confirm-failed (svg-tombstone and path-traversal-id).
• Targets the same merged feature; no behavior change outside the greenfield/repair paths.

[gemini-code-assist]

Code Review

This pull request introduces several enhancements and bug fixes: it resolves relative --browser paths against the run directory, tracks the exact mutation count of reverted batches to improve accept-rate metric accuracy, ensures rollback operations can detect and clean up newly created binary assets, and adds strict validation for feature IDs to prevent path traversal vulnerabilities. The reviewer's feedback suggests a valuable performance optimization in file-snapshot.ts to combine the separate text and binary file traversals into a single pass, reducing disk I/O by 50% in large workspaces, which subsequently allows for cleaning up the unused textFiles helper and its associated import.

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