chore(changelog): add Unreleased entry for PR #290 daemon MCP launch fix

[Copilot]

Adds a ### Fixed entry under [Unreleased] in CHANGELOG.md for PR #290, which fixed a silent daemon startup failure caused by daemon/manager.py launching the MCP server via the back-compat shim (python -m spellbook.mcp.server) instead of the package entry point (python -m spellbook.mcp).

Checklist

• Tests pass locally
• Documentation updated (if applicable)

Original prompt

Create a pull request in axiomantic/spellbook targeting main that adds an appropriate Unreleased changelog entry for the changes introduced by PR #290 (fix(daemon): launch MCP via spellbook.mcp package, not server shim).

Requirements:

• Inspect the repository's changelog/release-notes conventions and find the correct file and section for unreleased changes.
• Add a concise entry describing the PR fix(daemon): launch MCP via spellbook.mcp package, not server shim #290 change.
• Follow the repository’s existing formatting, categorization, and wording conventions.
• Do not make unrelated changes.
• Open the PR against main.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Please create a PR to main that adds an Unreleased changelog entry for the changes in @axiomantic/spellbook/pull/290

Assistant: I’ve started the PR creation flow and I’m waiting for your response to the approval prompt before I can continue.

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