[TheGreatAxios]

Summary

• Owner ruling: remove the echo workflow fixture. workflows/echo is deleted; @corbits/echo-workflow dropped from apps/hub/package.json and tsconfig.build.json.
• packages/workflows/src/catalog.ts and catalog.test.ts trimmed to the single Myra (assistant) entry.
• scripts/e2e/smoke-webhook.test.ts and scripts/e2e/walking-skeleton.test.ts rewired to deploy Myra's @corbits/assistant-workflow (buildAssistantWorkflow/serializeAssistantWorkflow) instead of the echo fixture. Since Myra's definition carries real toolPackagePins, walking-skeleton.test.ts's deploy loop now also calls publishCorbitsToolsRegistry before each deploy attempt, mirroring what smoke-webhook.test.ts already did.
• One-line doc cleanups in workflows/README.md and PRODUCT.md (docs/CHAT.md's "echo" mentions are about mention-handle de-duplication, unrelated to this workflow).

Test plan

• bun install
• bun run typecheck
• bun run lint
• bun run fmt
• bun test packages/workflows (98 pass, 1 pre-existing unrelated failure in unreachable-message-contract.test.ts — untouched by this change, a vendored-source drift check)
• bun test scripts/*.test.ts (70 pass, 1 skip for missing DATABASE_URL)
• scripts/e2e/smoke-webhook.test.ts / scripts/e2e/walking-skeleton.test.ts need DATABASE_URL to actually run; not exercised in this environment but typecheck/lint pass against the new Myra deploy path