[Routine - QP] fix: guard VersionManager against malformed history JSON shape

[winterdrive]

Pre-flight Check

Open PRs / active branches checked before selecting this target:

• [Routine - QP] fix: guard against non-array JSON in MCP clipboard history load #47 routine/qp-fix-mcp-clipboard-non-array-260706 — touches mcp-server/src/tools/clipboardTools.ts
• [Routine - QP] refactor: replace deprecated String.substr() in VersionHistoryService #46 routine/qp-fix-versionhistory-substr-260703 — touches src/services/VersionHistoryService.ts
• [Routine - QP] test: ignore local Claude worktrees in Jest #45 chore/ignore-claude-worktrees-jest — touches jest.config.js
• [Routine - QP] fix: close prefix-match bypass in PathUtils.validatePath #44 routine/qp-fix-path-traversal-prefix-260702 — touches src/core/PathUtils.ts, src/test/unit/pathUtils.test.ts
• [Routine - QP] fix: streamline quick create workspace routing #43 fix/quick-create-workspace-ux — touches src/commands.ts, src/promptProvider.ts, src/test/unit/promptProviderMultiroot.test.ts

This PR only touches src/core/VersionManager.ts and src/test/unit/versionManager.test.ts, which none of the above PRs modify, so there is no overlap.

Changes

VersionManager.loadHistory (the pure Node.js core version manager, distinct from VersionHistoryService.ts which #46 is fixing) parses *.history.json with a bare JSON.parse inside a try/catch. The catch only handles JSON.parse throwing (e.g. corrupted JSON) — it does not catch the case where parsing succeeds but produces the wrong shape (e.g. the file contains [1,2,3] or {} instead of { promptId, versions, currentVersionId }). In that case history.versions is undefined, and the very next line calling .find(...) elsewhere (getCurrentVersion, applyVersion, createVersion, etc.) throws a raw TypeError instead of falling back gracefully.

This mirrors the fix already merged for the sibling file VersionHistoryService.ts (commit 20b6a09, "guard VersionHistoryService against corrupted/malformed history JSON") — same bug pattern, same fallback strategy (reset to empty history), applied to the not-yet-patched VersionManager.ts.

• Added a VersionManager.isValidHistory type guard (same shape check as VersionHistoryService.isValidHistory).
• loadHistory now throws internally (caught by the existing catch block) when the parsed JSON doesn't match the expected shape, resetting to an empty history instead of letting a malformed shape propagate.
• Added two unit tests mirroring the existing VersionHistoryService corrupted-JSON tests: corrupted JSON text, and valid-but-wrong-shape JSON (an array).

Confirms this PR does not modify any MCP tool schema/names/parameters in mcp-server/src/tools/, and does not add/remove/update any dependencies.

Safety Verification

Commands run locally, all passed:

• npx tsc -p ./ — no errors
• npm run test:coverage (project's Jest command) — 7 test suites, 109 tests, all passed (includes the 2 new tests plus all pre-existing suites)

CI / Release Gate Note

This is a daily routine Draft PR. Package version bump (package.json/package-lock.json) and CHANGELOG.md updates are intentionally deferred to the weekend release/integration PR. If GitHub Actions fails only due to the repository's version-bump gate, that is expected release-readiness behavior for a routine PR, not a code validation failure.