feat: add PyPI publish workflow, release docs, and project metadata

[dgenio]

What changed

Implements PyPI publishing automation and release documentation per #37.

New files

• .github/workflows/publish.yml — Automated PyPI publish workflow triggered on v* tag push. Uses pypa/gh-action-pypi-publish with OIDC Trusted Publisher (no stored API tokens). Runs the full CI suite as a gate via reusable workflow call before publishing.
• RELEASE.md — Documents the complete release process: version bump, changelog update, tagging, what CI does, Trusted Publisher one-time setup, and versioning scheme.

Modified files

• .github/workflows/ci.yml — Added workflow_call: trigger so publish.yml can reuse CI as a gate job.
• pyproject.toml — Renamed PyPI package to weaver-kernel (Weaver ecosystem alignment). Added [project.urls] (Homepage, Repository, Documentation, Changelog). Added mcp and otel optional dependency groups.
• README.md — Updated pip install command to weaver-kernel.
• CHANGELOG.md — Added [Unreleased] entries for all changes.

Why

• No PyPI release exists — users can't pip install the package.
• No CI workflow for automated publishing on tag push.
• No documented release process.
• Package name agent-kernel conflicts with existing PyPI project; renamed to weaver-kernel to align with Weaver ecosystem (weaver-spec, contextweaver, ChainWeaver).

How verified

• ruff format — 35 files unchanged
• ruff check — only 2 pre-existing UP038 warnings (unrelated to this PR)
• mypy src/ — success, no issues in 20 source files
• pytest — 201 passed in 1.64s, 96% coverage

Acceptance criteria mapping

Criteria	Status
Tag push triggers automated publish workflow	✅ publish.yml triggers on v*
make ci gate prevents publishing broken code	✅ needs: ci reuses ci.yml
RELEASE.md documents the full release process	✅
Trusted Publisher configured (no API token secrets stored)	✅ id-token: write + environment: pypi; manual PyPI-side setup documented
Optional extras defined for future integrations	✅ mcp and otel extras added
pip install weaver-kernel works from PyPI	Requires tagging + PyPI Trusted Publisher setup

Notes

• PyPI Trusted Publisher requires a one-time manual configuration on pypi.org (documented in RELEASE.md).
• The first actual publish requires: git tag v0.2.0 && git push --tags after merging.
• AGENTS.md reviewed — no updates needed (doesn't reference package name or release workflows).

Closes #37

[Copilot]

Pull request overview

Adds automated PyPI publishing and release guidance, while updating project metadata to publish under the new weaver-kernel distribution name (issue #37).

Changes:

• Introduces a tag-triggered PyPI publish workflow that gates publishing on the existing CI workflow.
• Adds RELEASE.md documenting the end-to-end release process and Trusted Publisher setup.
• Updates pyproject.toml, README, and changelog to reflect the new PyPI distribution name and additional metadata/extras.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pyproject.toml	Renames distribution to weaver-kernel, adds project URLs, and adds mcp/otel optional dependency groups.
RELEASE.md	New release process documentation including Trusted Publisher (OIDC) setup steps.
README.md	Updates install command to pip install weaver-kernel.
CHANGELOG.md	Records unreleased entries for publishing workflow/docs/metadata rename.
.github/workflows/publish.yml	New workflow to build and publish on v* tags after CI gating.
.github/workflows/ci.yml	Enables reuse via workflow_call so publish workflow can invoke CI as a gate.

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