Check Behavior Annex dispatch timeouts for every source 🤖

[lwrage]

Summary

• check dispatch-relative timeout uniqueness for every source produced by a multi-source transition
• replace the misleading duplicate diagnostic with a state-specific D.4(L1) message
• preserve legal multi-source declarations and once-per-declaration Timed/Period validation

Fixes #3267

Cause and correction

The strict translator expands a multi-source declaration into one transition per source, but the driver deduplicates the shared dispatch condition by its declarative origin. Only the first expanded source therefore reached D_4_L1_Check.

The checker now records dispatch-relative timeout ownership for each expanded complete source before shared-condition deduplication. A second timeout reports the affected state, while protocol and Period checks continue to run once per written condition. Because CompletionRelativeTimeout extends DispatchRelativeTimeout, the driver tests the completion-relative case first so the #3266 rule remains independent.

Regression coverage

Issue3267Test validates three external model fixtures:

• two separate dispatch-relative timeouts from one state report exactly one duplicate diagnostic naming that state
• overlapping multi-source declarations report exactly one diagnostic naming their shared state
• distinct complete states may each have one timeout without diagnostics

The fixtures include diagnostics, resolved-model, source-position, and unparse characterization goldens.

Validation

• focused Issue3267Test: 3 tests, 0 failures, 0 errors
• Issue3154Test: 7 tests, 0 failures, 0 errors
• CoveringSemanticTest: 11 tests, 0 failures, 0 errors
• complete org.osate.ba.tests bundle: 231 tests, 0 failures, 0 errors
• clean root reactor with -Dtycho.localArtifacts=ignore: 143 modules, build success

Dependency and residual risk

This PR is stacked on #3276 and must merge after it. It reuses #3276's per-expanded-source uniqueness boundary, then adds the dispatch-relative branch. Grammar, metamodel, generated sources, and serialization logic are unchanged.