Draft unreleased release notes

[marcus]

Summary

• Add an Unreleased changelog section for post-v0.3.4 changes.
• Cover the --max-projects scheduling fix, mobile docs nav fix, and development pre-commit hook.

Verification

• git diff --check
• go vet ./... (via pre-commit hook)
• go build ./... (via pre-commit hook)
• Go tests skipped: docs-only change

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Automated by nightshift