chore(release): bump version to 0.7.0

[lostmartian]

What

Bumps all three distributables to 0.7.0 and cuts the changelog section for #67, which adds OpenAI Codex CLI support.

File	Version
src/agentdiff/__init__.py (PyPI agent-trajectory-diff)	0.6.2 → 0.7.0
npm/package.json (npm @kerrshift/agentdiff)	0.6.2 → 0.7.0
plugins/agentdiff/.claude-plugin/plugin.json	0.6.2 → 0.7.0

Why

Ships Codex support, so agentdiff covers Claude Code and Codex in one report. This is a minor bump because it adds new reading capability and new --agent / --codex-home options; no existing behaviour changes. Roadmap: P1.4.

How

After merge, pushing the v0.7.0 tag runs publish.yml in this order:

1. build;
2. PyPI;
3. npm, with provenance;
4. GitHub release.

Testing

make lint                  -> All checks passed
uv run python -m pytest    -> 475 passed (three-way version-sync test included)
cd npm && npm test         -> 4 passed
uv build                   -> agent_trajectory_diff-0.7.0 wheel + sdist

Known gap: Codex parsing is tested on synthetic rollouts built from the openai/codex rust-v0.163.0 schema. No real Codex session has been run through it yet.

Checklist

• Exactly one logical change in this PR
• make lint passes
• uv run python -m pytest is green
• Docs updated if user-facing
• CHANGELOG.md entry added under [Unreleased] (if feat/fix)
• Conventional title: type(scope): summary