Release v0.3.0

Added
- **Multi-user Architecture**: Journal filenames now include the system user (``$USER``) to prevent Git merge conflicts on shared ledgers.
- **Agent Identity Hash**: Agent identifiers now automatically extract and append a short hash of the conversation ID from ``ANTIGRAVITY_SOURCE_METADATA``.
- **Tidy Command**: Introduced ``ajourn tidy`` to intelligently parse, standardise, and de-duplicate log entries.
Changed
- **Git Ignore Protocol**: Updated ``.gitignore`` to track ``.agents/journal/entries/`` for shared team state, while strictly ignoring the volatile ``state.json``.
- **SDK Migration**: Migrated CLI variable checks from ``GEMINI_AGENT_NAME`` to ``ANTIGRAVITY_AGENT_NAME`` to support the Google Antigravity SDK.
- **GNUmakefile Prefix**: Modified ``PREFIX`` to default to ``$(HOME)/.local`` for safer user-level installations without ``sudo``.
- **Release Protocol**: Updated ``docs/technical/release.rst`` to include mandatory ``CHANGELOG.rst`` updates and document the automated note extraction process.
Fixed
- **Make Install Target**: Replaced ``$(PWD)`` with ``$(CURDIR)`` in ``GNUmakefile`` to ensure standard ``make -C`` behavior.
- **Test Isolation**: Explicitly unset ``ANTIGRAVITY_SOURCE_METADATA`` during testing to prevent live agents from polluting mocked environments.
- **Hook Configuration**: Corrected invalid ``TurnEnd`` hook to ``AfterAgent`` and migrated ``type: prompt`` to ``type: command`` in documentation.
Security