#8774: Fix/frontend session key normalization

Problem The frontend session key input validation was overly restrictive, only accepting the three-segment agent:agentId:sessionKey format. However, the backend session key parsing logic actually supports multiple format types: Three-segment: agent:agentId:sessionKey (e.g., agent:main:xiaohua) Two-segment: subagent:xxx, acp:xxx (e.g., subagent:test, acp:project) Special cases: main, global, unknown Other two-segment formats: For extensibility This mismatch between frontend validation and backend parsing logic caused: Format inconsistency: Users couldn't input valid session keys that the backend supports Poor user experience: Confusing error messages for legitimate formats System limitations: Prevented users from using valid session key types like subagent: and acp: Solution Updated the frontend validation logic to match the backend's actual session key parsing requirements: ✅ Supported Formats agent:agentId:sessionKey - Requires exactly 3 segments subagent:xxx - Requires at least 2 segments acp:xxx - Requires at least 2 segments Other two-segment formats - For future extensibility Special single-segment cases: main, global, unknown 🔧 Implementation Details Format-specific validation: Different prefixes have different segment requirements Visual feedback: Red border and specific error messages for invalid formats Connection control: Disable connect button until format is valid User guidance: Updated placeholder and tooltip with supported format examples 🎯 Validation Examples Valid inputs: ✅ agent:main:xiaohua ✅ agent:claude:work ✅ subagent:test ✅ acp:project ✅ telegram:chat ✅ main ✅ global Invalid inputs: ❌ xiaohua (single segment, not special case) ❌ agent:main (agent format missing third segment) ❌ subagent: (missing content after colon) Testing ✅ Build passes successfully ✅ Gateway restart successful ✅ No linting errors ✅ Validation logic matches backend parsing in src/sessions/session-key-utils.ts Impact Improved UX: Users can now input all valid session key formats System consistency: Frontend validation aligns with backend parsing logic Better error handling: Specific error messages guide users to correct formats Future-proof: Supports extensibility for new session key types This fix ensures the frontend enforces proper session key formats while supporting all the formats the backend actually accepts, eliminating confusion and improving the overall user experience. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates the Control UI’s “Default Session Key” input to accept the backend-supported session key formats (3-part `agent:agentId:…`, 2-part prefixed keys like `subagent:`/`acp:`, and special single-token keys), adds inline validation messaging, and disables the Connect button until the value is considered valid. The change is localized to `ui/src/ui/views/overview.ts` and aims to align frontend validation UX with backend session key parsing (`src/sessions/session-key-utils.ts`). <h3>Confidence Score: 4/5</h3> - This PR is generally safe to merge; issues are limited to minor frontend/backend validation mismatches that can block some inputs unnecessarily. - Changes are UI-only and straightforward, but the new validation is slightly stricter/different than backend parsing in a couple edge cases (case sensitivity for special tokens; handling of empty segments). These are unlikely to break existing flows broadly but could frustrate some users. - ui/src/ui/views/overview.ts <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} <!-- /greptile_comment -->