feat: generate v1 API client from OpenAPI

[EastSun5566]

What

• Generate @hackmd/api/raw from the v1 OpenAPI spec with @hey-api/openapi-ts. The existing API class remains the only handwritten convenience layer and delegates to generated operations; users do not need to switch clients.
• Cover all 59 v1 operations and fix retry isolation.
• Generate and export an operation registry from the same spec, so the CLI can discover operations offline and call the raw API.
• Derive public response types from OpenAPI, correcting handwritten mistakes such as note createdAt and lastChangedAt being typed as string instead of number.
• Support nullable team owners and description: null to clear personal/team note metadata. Note GET descriptions remain strings.

Documentation

• TypeDoc builds a static API reference from the public API and @hackmd/api/raw types (pnpm docs:build).
• The Pages workflow deploys it on pushes to master. Before the first deployment, set Settings → Pages → Build and deployment → Source: GitHub Actions in this repository.

Related work

• CLI issue #118 PR #119 adds generic v1 commands using @hackmd/api/raw.

Checks

• Generated-code check, typecheck, 113 unit tests, build, and TypeDoc pass.
• All 12 existing live E2E tests previously passed against production with HACKMD_E2E_MUTATIONS=1. The new nullable-description contract is covered by local tests.

Regeneration

After the updated v1 OpenAPI spec is live at api.hackmd.io, run from nodejs/:

pnpm spec:pull
pnpm codegen
pnpm check:generated

Commit spec/hackmd-openapi.json and src/generated/ together, then rerun CI.

Fixes #61 #60

[EastSun5566]

types gen docs: