Add a project-level version bumping mechanism for punkshell, tracked in
punkproject.toml, independent of individual module versions.
- root AGENTS.md: new 'Project Versioning' section with change-driven
SEMVER bump policy (patch/minor/major triggers), CHANGELOG.md requirement,
advisory enforcement contract, and independence from module versions.
- src/AGENTS.md: cross-reference to root Project Versioning section so
agents working in src/ discover the rule during their DOX chain walk.
- CHANGELOG.md: new repo-root file with initial 0.2.0 entry; latest
'## [X.Y.Z]' header must match punkproject.toml version.
- src/make.tcl: new 'projectversion' subcommand — read-only, advisory check
that warns on CHANGELOG/punkproject.toml version mismatch and on src/
commits since the last punkproject.toml change. Exempt from bootsupport
staleness abort (same as 'check'). Self-contained Tcl, no punk deps.
Assisted-by: harness=opencode; primary-model=openrouter/z-ai/glm-5.2; api-location=openrouter.ai