chore: bump to 0.6.1

[eaitbrahim]

Patch bump — packaging and docs only, no behaviour change. Bumps the root distribution, all five workspace packages, every intra-workspace pin, and uv.lock.

Why this release matters more than a patch usually does

0.6.0's deploy exposed that the documented install upgraded keel_trader alone and silently left the siblings behind. The real deployment was found running keel-trader 0.5.7 against keel-core 0.5.5 — two releases stale — because the dependencies were unpinned, and keel --version reports only the keel-trader distribution so it could not see the mismatch.

#243 fixed that. This is the first release whose wheels carry the pins, which makes it the first self-correcting install:

Requires-Dist: keel-core==0.6.1
Requires-Dist: keel-broker-api==0.6.1
Requires-Dist: keel-broker-coinbase==0.6.1

Verified by reading the built wheel's METADATA, not assumed.

The new packaging test did its job on this very bump

Bumping the root version alone failed it twice before the pins were updated:

FAILED test_every_workspace_package_carries_the_same_version
FAILED test_workspace_siblings_are_pinned_to_the_exact_version[keel-trader]

That is precisely the silent failure it was written to catch.

Gates, run locally on this branch

ruff              All checks passed!
mypy              Success: no issues found in 224 source files
pytest            2696 passed, 1 skipped
migration_smoke   fresh and downgraded both reach schema 10
live template     mode=confirm
wheel metadata    Requires-Dist pins present at 0.6.1

After merge

1. Dispatch release.yml with 0.6.1
2. Reinstall in ~/keel per the corrected README flow
3. keel versions must exit 0 — that is the check 0.6.0 could not perform

No schema change (both DBs already at 10), so no migration this time.