Adopt preferred repository-scoped REST routes

[necolas]

Why

Notion could not use the canonical repository delete route during integration because the docs described that route while the SDK still called a deprecated /api/v1 route. The same integration exposed confusion between a public repository name and an internal repository ID.

Credential operations need a repository name on the canonical repository-scoped route, while the legacy create operation accepts an internal repository ID. Reusing the old field for the new meaning would silently change existing programs.

Scope

• Move preferred operations to unversioned /api routes and repository-scoped /api/repos/{repo_name} routes.
• Encode repository names exactly once as one path segment while keeping the raw name in the JWT claim.
• Add preferred credential repoName options across TypeScript, Python, and Go.
• Let preferred create calls use repoName and omit repo_id.
• Preserve the exact legacy create route and body when a caller supplies repoId.
• Preserve the old update and delete request shape when repoName is absent.
• Keep apiVersion as an accepted deprecated no-op.
• Add a route guard that restricts legacy route strings to one compatibility helper per language.
• Update tests, package documentation, skills, and release notes. This supersedes Adopt canonical unversioned API paths across SDKs #49 without changing the meaning of repoId.

Tradeoffs

• Legacy credential calls remain available for source compatibility even where the current service rejects the old route.
• Added Go struct fields can break external unkeyed composite literals. Keyed literals remain compatible.
• TypeScript uses overloads to preserve the existing interface contract during the migration.

Blast Radius

This changes HTTP routes for preferred calls in all three SDK packages. Legacy credential input keeps its previous wire behavior.

This PR is stacked on #47. Merge #47, retarget this PR to main, and require the main-branch CI result before merge. Package versions and public documentation follow in the release work.

Verification

• TypeScript: 262 tests, package build, compatibility type compilation, and full-workflow help pass.
• Python: 199 tests, Ruff checks, Ruff format, and mypy pass.
• Go: package tests pass.
• The legacy-route guard and its 13 tests pass.
• Git diff and secret checks pass.
• Current GitHub security checks pass.
• The live workflow was not run because no test cluster or GIT_STORAGE_KEY_PATH was available.

[notion-workspace]

Update SDK to use non-deprecated HTTP API