Compat baseline 5/5: publish a distinct, traceable supported-baseline version #135

Effort: S

Part of #102. Last: depends on 1/5, 3/5 and 4/5. This is a maintainer decision plus a release action.

Version strings are reused across many commits, so a user cannot tell which build is compatible. Publish a baseline that can be identified from its release or commit.

Scope

• Choose the baseline: e5339c0 or a tested descendant is the candidate named in Define a verifiable core compatibility baseline for current plugins #102; it is not yet certified.
• Publish a distinct version/tag for it (do not reuse 0.3.0-alpha.2).
• Update the compatibility matrix and minHost guidance to reference it.

Acceptance criteria

• A user can identify a compatible build from its release or commit.
• An incompatible feature explains its missing requirement before use.
• Tested host and plugin revisions are recorded in the matrix.

Out of scope

Back-certifying older builds.