chore(deps): optional core extra pinned to v0.5.8

[fivepanelhat]

Sprint B — lock Sprint A soft seams

What

• New optional extra: pip install "aether[core]" → Core v0.5.8
• Included in aether[all]
• Still soft-import: without the extra, SessionEvent + provider profile bridges no-op safely

Install

pip install "aether[core]"
# or
pip install "aether[all]"

Links

• Core release: https://github.com/fivepanelhat/Coastal-Alpine-Core/releases/tag/v0.5.8
• Branch: https://github.com/fivepanelhat/Aether/tree/chore/optional-core-v0.5.8
• pyproject: https://github.com/fivepanelhat/Aether/blob/chore/optional-core-v0.5.8/pyproject.toml
• Phase 1: feat(session-audit): SessionEvent soft bridge — Sprint A Phase 1 #51
• Phase 2: feat(llm): soft Core provider profile bridge — Sprint A Phase 2 #52
• Weaver companion pin: chore(deps): pin Core to v0.5.8 + Sprint A architecture notes Weaver#39 (if numbered)