Reject duplicate Behavior Annex completion-relative timeouts 🤖

[lwrage]

Summary

• reject a second outgoing completion-relative timeout from the same complete state
• check every source produced by a multi-source transition expansion without repeating declaration-level validation
• add external AADL regressions for separate duplicates, overlapping multi-source declarations, and a legal distinct-source control

Fixes #3266

Cause and correction

D_4_L2_Check queried a Map<BehaviorState, BehaviorTransition> with the entire source-state list, although entries were stored under individual states. Separately written duplicate timeouts therefore never matched. Multi-source conditions are shared across strict transition expansions and intentionally validated once, which also skipped uniqueness checks for non-first sources.

The checker now records completion-relative timeout ownership for each expanded complete source state before shared-condition deduplication. Period/value and other declaration-level checks still run once per written condition.

Regression coverage

Issue3266Test validates three external model fixtures:

• two separate timeout transitions from one state report exactly one D.4(L2) error on the second timeout
• overlapping multi-source declarations report exactly one error at their shared state
• distinct complete states may each have one timeout without diagnostics

The fixtures include the standard diagnostics, resolved-model, source-position, and unparse characterization goldens. Existing covering-syntax goldens now record the two newly detected duplicate timeout transitions.

Validation

• focused Issue3266Test: 3 tests, 0 failures, 0 errors
• CoveringSemanticTest: 11 tests, 0 failures, 0 errors
• Issue3184Test: 5 tests, 0 failures, 0 errors
• complete org.osate.ba.tests bundle: 228 tests, 0 failures, 0 errors
• clean root reactor with -Dtycho.localArtifacts=ignore: 143 modules, build success

Dependencies and residual risk

This PR is based directly on current master after #3274 and #3275 and has no PR dependency. The change is confined to BA legality checking and its regression assets; grammar, metamodel, generated sources, and serialization logic are unchanged.