docs(release): add mcp-publisher validate pre-tag check + backfill phase issue links

[ayhammouda]

Summary

Two small housekeeping items after the v0.1.5 → v0.1.6 release arc:

1. .github/RELEASE.md — new pre-tag check

The Pre-Release Verification checklist now includes:

```bash
curl -L "https://github.com/modelcontextprotocol/registry/releases/latest/download/mcp-publisher_..." | tar xz mcp-publisher
./mcp-publisher validate server.json
```
Must report `✅ server.json is valid`.

Why: v0.1.5 was a half-publish — PyPI succeeded (no description-length limit; 152-char description accepted) but MCP Registry rejected validation (its schema caps description ≤ 100 chars). The recovery took an extra v0.1.6 patch release. A 10-second local validate before tagging would have caught it.

2. .planning/ROADMAP.md — backfill phase issue links

The post-v0.1.5 backlog table now links the three phase rows to live GitHub issues:

Phase	Issue
09 `compare_versions`	#32
10 `whatsnew_for_version`	#33
11 `detect_python_version` v2	#34

All three issues use the new `phase-plan` label + `help wanted` + `enhancement`, with the corresponding CONTEXT.md content as the issue body.

Out of scope

The RELEASE.md still has stale per-version content (header says "v0.1.1 Release Checklist", grep checks for `0.1.1` in pyproject.toml, etc). Generalizing those to be version-agnostic is a worthwhile cleanup but separate from this fix-and-backfill PR. Suggest a follow-up issue if desired.

Test plan

• `./mcp-publisher validate server.json` on this branch → `✅ server.json is valid` (verified locally against the live registry endpoint before commit)
• Issue links resolve: phase 09 — compare_versions(symbol, v1, v2) #32, phase 10 — whatsnew_for_version(version) #33, phase 11 — detect_python_version v2 (venv-aware) #34
• CI green
• Reviewer can follow the new pre-tag check successfully

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Updated release process documentation with server validation requirements during releases.
  • Updated roadmap with specific tracking references for upcoming features and enhancements.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between f948f09 and c26d1fd.

📒 Files selected for processing (2)

• .github/RELEASE.md
• .planning/ROADMAP.md

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📝 Walkthrough

Walkthrough

This PR updates two planning and documentation artifacts. The release checklist gains a validation step for server.json schema compliance before tagging. The roadmap backlog replaces TBD placeholders with concrete GitHub issue links for three upcoming tool enhancements.

Changes

Documentation and Planning Updates

Layer / File(s)	Summary
Release validation checklist step .github/RELEASE.md	Added checklist instruction to run mcp-publisher validate server.json against the live MCP Registry schema, with expected success output and guidance to shorten description on main if validation fails.
Roadmap issue linking .planning/ROADMAP.md	Updated Backlog rows for phases 09–11 to replace "#TBD-link-after-PR-merges" with concrete issue references (#32, #33, #34) for upcoming tool features.

🎯 1 (Trivial) | ⏱️ ~3 minutes

🐰 Two checklist steps we compile,
A roadmap now linked, clean and simple,
No code to review, just guides refined,
Release and planning, both aligned!

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/release-runbook-and-phase-issues

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