Release 0.3.0

Added

• Display overlay in SkillMapper (§5.13) — to_skill() reads metadata["display"]["a2a"] for skill name, description, tags, and guidance.
• Skill name: a2a.alias → display.alias → humanized module_id.
• Description: a2a.description → display.description → module.description. Guidance appended if present.
• Tags: display.tags → module.tags.

Changed

• apcore dependency bumped from >=0.9.0 to >=0.14.0.
• Environment variables renamed with APCORE_ prefix: JWT_SECRET → APCORE_JWT_SECRET, A2A_EXECUTION_TIMEOUT → APCORE_A2A_EXECUTION_TIMEOUT.

Removed

• _build_extensions() dead code — AgentSkill has no extensions field in the A2A SDK; this method could never be wired in. Deleted along with its 3 tests.

Tests

• 6 display overlay tests + 3 empty-string fallthrough tests for cross-language parity with TypeScript.
• Removed 3 test__build_extensions_* tests (dead code).

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