Add exact branch and tag lookup

[necolas]

Summary

• add exact branch and tag lookup to the TypeScript, Python, and Go SDKs
• use the preferred repository-scoped routes with exact query encoding and git:read
• keep exact results separate from list pagination and private tag fields
• update package docs, release notes, the SDK skill, and route guards

Stack and release sequence

This PR is stacked on #50, which is stacked on #47.

Use this release sequence:

1. Merge feat(sdk): adopt standard API vocabulary #47 and Adopt preferred repository-scoped REST routes #50.
2. Publish the feat(sdk): adopt standard API vocabulary #47/Adopt preferred repository-scoped REST routes #50 additive deprecation release.
3. Complete monorepo PR #2400 as the only companion docs PR for that release.
4. Retarget this PR to main, then merge and publish it as a later, separate additive SDK release.
5. Complete monorepo PR #2401 as the only companion docs PR for this later release.

Do not merge this PR before the #47/#50 release and monorepo PR #2400 are complete.

This PR excludes #51. It also excludes version changes, releases, and monorepo catalog changes.

Compatibility note

This PR adds methods to the exported TypeScript Repo interface and Python Repo protocol. External custom implementations, mocks, or adapters can fail type checks until they add these methods. The owner must accept this source-compatibility effect or choose a separate capability interface before publication.

Verification

• pnpm --filter @pierre/storage exec vitest --run — 270 tests passed
• pnpm build — passed
• pnpm exec tsc --project tsconfig.type-tests.json — passed
• node tests/full-workflow.js --help — passed
• ./venv/bin/pytest -v — 205 tests passed
• ./venv/bin/ruff check pierre_storage — passed
• ./venv/bin/ruff format --check pierre_storage — passed
• ./venv/bin/mypy pierre_storage — passed
• gofmt check — passed
• go test ./... — passed
• python3 scripts/check_legacy_routes.py — passed
• python3 -m unittest discover -s scripts/tests -v — 13 tests passed
• moon run :test — all three SDK projects passed
• git diff --check, conflict-marker check, and secret-pattern scan — passed

The live workflow did not run because this environment has no GIT_STORAGE_KEY_PATH.

[notion-workspace]

Add getBranch and getTag to SDK