feat: add persona context to delivery messages

[mrgoonie]

Summary

• pass compact active-agent persona brief into generated quick ack and intermediate delivery requests
• add delivery prompt persona guidance only when a brief exists
• reject generated delivery text that mentions internal context/system-prompt/tool/provider details while keeping fixed templates unchanged

Closes #166

Verification

• /usr/local/go/bin/go test -count=1 ./internal/channels ./internal/agent ./cmd
• /usr/local/go/bin/go test ./...
• /usr/local/go/bin/go build ./...
• /usr/local/go/bin/go build -tags sqliteonly ./...
• /usr/local/go/bin/go vet ./...
• TEST_DATABASE_URL=postgres://postgres:test@localhost:5433/goclaw_test?sslmode=disable /usr/local/go/bin/go test -count=1 -race -tags integration ./tests/integration/

[mrgoonie]

review-pr --fix --reply result:

• Iterations: 1 review/fix cycle after initial implementation review
• Commits pushed: a76f443 feat: add persona context to delivery messages
• Final verdict: Approve
• Merge state: CLEAN
• CI: green (go, web, release-versioning all passed)
• Remaining findings: none
• Blockers/questions: none