[docs] Formalize the SemVer tag and daily release policy #271

Goal

Write the existing OpenDirector tag and daily release practice into the repository so cuts are not only tribal knowledge.

Current published tags: v0.1.0, v0.1.1, and v0.1.2, each with a GitHub Release. In-tree version fields stay at the last cut (currently 0.1.2) until the next one lands.

Related: #7 (release readiness go/no-go). This issue does not replace #7.

Policy to record

1. Public tags use SemVer with a v prefix: vMAJOR.MINOR.PATCH. Do not introduce a second public stream (CalVer, date tags, or nightly tags).
2. Daily patch cuts stay on v0.1.x around 04:00 Asia/Shanghai after the ~02:00 nightly, when there are merges since the last tag and Release checks plus the last nightly gate-parity are green. Skip if there are no merges, or if that gate is red or still running. Advisory nightly lanes (browser-production, browser-extended, perf-outputs) do not block.
3. Do not tag every merge. The cut is one tag after that day's landed work, plus a version-bump PR that aligns npm/package-lock, pyproject.toml, local API OpenAPI, DeepSeek ACP clientInfo, and the Claude plugin manifest (same set as [build] bump the release version to 0.1.2 #248 / [build] bump the release version to 0.1.1 #204).
4. Bump MINOR only for a named milestone. Bump MAJOR only when declaring a supported public product (v1.0.0).
5. Each published tag is immutable, points at one main SHA (after the version-bump PR), and ships a GitHub Release with English notes listing merges since the previous tag. Do not retag, and do not create a floating latest git tag.
6. Nightly CI is a gate, not a public release. If installable nightlies are added later, they must be GitHub prereleases (for example v0.1.3-nightly.YYYYMMDD) and must not become the repository's latest release.

Deliverable

• Add docs/development/release.md with the policy above, short and operational.
• Link it from docs/README.md (development process). A short pointer from CONTRIBUTING.md and/or [RFC] First release scope and readiness checklist #7 is welcome if it stays a link, not a second copy.
• English only for the new doc and this issue.

Acceptance

• The policy is in the repository and discoverable from the docs index.
• It matches the current daily cut practice and does not invent a second tag family.
• Version-field alignment and the Release/nightly gate are stated clearly.
• Documentation-only change; no unrelated test or code churn.