feat(miner-foundation): scaffold packages/gittensory-engine package skeleton

[JSONbored]

Stand up the new shared engine package packages/gittensory-engine/ (npm name @jsonbored/gittensory-engine) that will house deterministic logic extracted from src/ in later issues. This issue is packaging-only — no logic moves yet. Mirror the existing packages/gittensory-mcp/ conventions exactly: its package.json shape (license, repository.directory, publishConfig.access: public, engines.node >=22.0.0), its tsconfig approach, and its build script pattern (node --check per emitted file, extended here to a real tsc build since this package is pure TS logic, not a JS CLI).

Deliverables

• packages/gittensory-engine/package.json — name @jsonbored/gittensory-engine, version 0.1.0, AGPL-3.0-only license, type: module, repository.directory: packages/gittensory-engine, files list scoped to dist + CHANGELOG.md (no src).
• packages/gittensory-engine/tsconfig.json extending the repo's compiler options (strict, noUncheckedIndexedAccess, exactOptionalPropertyTypes — match root tsconfig.json) with its own outDir: dist.
• packages/gittensory-engine/src/index.ts placeholder barrel export (empty re-export block with a comment marking it as the extraction target for later issues).
• A build script (tsc -p tsconfig.json) and confirm npm run build --workspace @jsonbored/gittensory-engine succeeds against the placeholder.
• Root package.json already globs packages/* via its workspaces field — verify npm ci picks up the new package with no additional wiring, and note that in a comment/README.
• packages/gittensory-engine/README.md stub explaining the package's purpose (shared deterministic logic for both the review-stack backend and gittensory-miner) and that it is versioned independently.

References

• packages/gittensory-mcp/package.json — the packaging convention to mirror (name, bin, files, engines).
• packages/gittensory-mcp/bin/gittensory-mcp.js — sibling package's entry-point style (for later CLI issues, not this one).
• Root package.json workspaces: ["apps/*", "packages/*"] — confirms the new package is auto-discovered.
• Root tsconfig.json — the compiler options to extend.
• New path: packages/gittensory-engine/ (this issue creates it).

[linear-code]

JSO-2372