release: v0.10.6 — version bump so the release gate can pass

[Rome-1]

Why this exists

Five fixes are already merged to main (#264, #265, #266, #267, #268) and cannot ship, because the release gate added in #256 correctly refuses to publish a version that is already on the registry. main still says 0.10.5, and npm and PyPI already serve 0.10.5. The bump is the only thing standing between main and a release.

Verified both directions before opening this:

./scripts/check-version-unpublished.sh 0.10.6   ->  exit 0   (ok: not published, both registries)
./scripts/check-version-unpublished.sh 0.10.5   ->  exit 1   (correctly refuses)

What 0.10.6 ships

All five already merged to main:

• Unhandled errors no longer print your API key (fix(python): do not render local variables in tracebacks #264). A command that failed with an unhandled exception could include the key and other local values in its traceback. Tracebacks now print without local variables.
• A project's .env can no longer supply Rafter's own settings (fix: never take RAFTER_* settings from a project .env #265). Previously a .env in the working directory could override RAFTER_API_KEY and other RAFTER_* settings you configured yourself. Behavior change: if you relied on RAFTER_API_KEY in a project .env, move it to your shell environment or ~/.rafter/config.json — the CLI will now report the key as missing if .env was its only source.
• rafter run now checks that an auto-detected branch has been pushed before scanning it (fix(run): refuse an auto-detected branch that is not on the remote #266). Running without --branch from a branch that doesn't exist on the remote used to queue a scan that failed later with a "branch not found" error; it now fails fast with a clear message.
• rafter secrets --diff / rafter agent scan --diff reject an option-shaped ref before it reaches git (fix(secrets): reject a --diff ref that starts with "-" #267). A --diff value starting with - could previously be misread by git as an option rather than a ref.
• rafter agent init --local --with-gemini no longer runs through a shell (fix(node): pass paths to child processes as arguments, not shell strings #268). A path containing shell metacharacters could previously have part of it executed during skill registration.

Order of operations

This PR only lands the bump on main. Merging it does not publish anything. The promote PR (main -> prod) is what publishes, and it cannot go green until this is on main. The promote PR is already open and will go green once this merges.

After the promote merges, check the registry, not the job: npm view @rafter-security/cli version must read 0.10.6.

Checks run locally

• tsc --noEmit: clean
• Node build (pnpm run build): clean
• Node test suite (vitest run, capped workers, serial files): 2313 passed, 9 skipped, 7 failed — the 7 failures are pre-existing and environment-specific to this box, not caused by this branch: verified by running the identical test files against unmodified origin/main and getting the same 7 failures (stale system python3 editable install reporting 0.9.0 from an unrelated checkout, and a pre-existing ~/.rafter/config.json / ~/.cursor state that no CI runner has). 3 of the 7 are the known Cursor-hook failures already called out in fix: never take RAFTER_* settings from a project .env #265-fix(node): pass paths to child processes as arguments, not shell strings #268.
• Python test suite (pytest tests/, isolated HOME): 1757 passed, 1 skipped, 0 failed
• scripts/check-version-unpublished.sh 0.10.6: passes for both npm and PyPI