docs: define the 1.x compatibility policy for catalog, behavior, and output changes

[e54-bot]

Fixes #313

Summary

Records how catalog, parse/validation/emit, and API changes are versioned under 1.x, in docs/compatibility-facades.md, and links it from the semver section of docs/release.md.

Decisions (maintainer)

• Removed ids. Catalog corrections of never-native ids (the feat(catalog)!: retire non-native ids forcePlayerHero, stopForcingHero, forceThrottle, stopChasingVariable, isFiringSecondaryFire #299 kind) are minor releases, and the parser rejects the id afterwards. Overwatch has never removed a native Workshop action or value, so no legacy-id support is added. If it happens, the release notes declare it a breaking behavior change and the maintainer decides then between a minor and a major release.
• Release notes. GitHub Release notes come from --generate-notes, i.e. merged PR titles. Catalog updates use feat(catalog). Other changes to parse/validation/emit results use feat(<area>) with a ## Behavior change section in the PR body. fix is kept for patch-level changes. No tooling change is needed, because release-plz already derives a minor release from feat.

Review points

• Patch is defined strictly: any change observable in Program, emitted text, validation results, or catalog content is minor. Most past fix(parser|emitter|catalog) PRs would be feat under this rule.
• The acceptance criterion "the next release uses it" can only be checked on the release after this merges.

Verification

Documentation-only change; maintainer review is the completion check. git diff --check passes, and the new anchor link from release.md matches the heading.