Keep local clawhip artifacts from tripping routine repo work

Dogfooding kept reproducing OMX team merge conflicts on
`.clawhip/state/prompt-submit.json`, so the init bootstrap now
teaches repos to ignore `.clawhip/` alongside the existing local
`.claw/` artifacts. This also updates the current repo ignore list
so the fix helps immediately instead of only on future `claw init`
runs.

Constraint: Keep the fix narrow and centered on repo-local ignore hygiene
Rejected: Broader team merge-hygiene changes | unnecessary for the proven local root cause
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: If more runtime-local artifact directories appear, extend the shared init gitignore list instead of patching repos ad hoc
Tested: cargo fmt --all --check
Tested: cargo clippy --workspace --all-targets -- -D warnings
Tested: cargo test --workspace
Tested: Architect review (APPROVE)
Not-tested: Existing clones with already-tracked `.clawhip` files still need manual cleanup
Related: ROADMAP #75

.gitignore

@@ -8,4 +8,5 @@ archive/
 # Claw Code local artifacts
 .claw/settings.local.json
 .claw/sessions/
+.clawhip/
 status-help.txt