#17897: refactor: extract firstDefined utility from telegram/line/slack

## Summary - Problem: `firstDefined<T>(...values)` utility duplicated identically in 3 files across telegram, LINE, and slack channel modules (3 definitions, 14 call sites). - Why it matters: Identical utility logic copied per-channel increases maintenance surface and risks divergence. - What changed: Extracted `firstDefined` to `src/utils.ts` and updated all 8 consumer files to import from the shared location. - What did NOT change (scope boundary): Channel-specific logic (`normalizeAllowFrom`, `isSenderAllowed`) remains in each channel's `bot-access.ts` — those have intentional behavioral differences per channel. ## Change Type (select all) - [ ] Bug fix - [ ] Feature - [x] Refactor - [ ] Docs - [ ] Security hardening - [ ] Chore/infra ## Scope (select all touched areas) - [ ] Gateway / orchestration - [ ] Skills / tool execution - [ ] Auth / tokens - [ ] Memory / storage - [x] Integrations - [ ] API / contracts - [ ] UI / DX - [ ] CI/CD / infra ## Linked Issue/PR - Related #17770 #17793 #17865 #17878 #17887 (cross-channel dedup refactor series) ## User-visible / Behavior Changes None ## Security Impact (required) - New permissions/capabilities? `No` - Secrets/tokens handling changed? `No` - New/changed network calls? `No` - Command/tool execution surface changed? `No` - Data access scope changed? `No` ## Repro + Verification ### Environment - OS: macOS (darwin) - Runtime/container: Node 22+ / Bun - Model/provider: N/A (refactor) - Integration/channel (if any): Telegram, LINE, Slack ### Steps 1. `corepack pnpm tsgo` — type check passes 2. `corepack pnpm build` — build passes 3. `corepack pnpm test -- src/telegram/bot.test.ts src/telegram/bot/helpers.test.ts src/telegram/bot-message-context.dm-threads.test.ts src/line/bot-handlers.test.ts src/slack/monitor/monitor.test.ts` — 81 tests pass ### Expected - All tests pass, no behavior changes ### Actual - 5 test files, 81 tests, all pass ## Evidence - [x] Failing test/log before + passing after - [x] Trace/log snippets ``` ✓ src/line/bot-handlers.test.ts (4 tests) 55ms ✓ src/telegram/bot/helpers.test.ts (26 tests) 4ms ✓ src/slack/monitor/monitor.test.ts (16 tests) 36ms ✓ src/telegram/bot.test.ts (30 tests) 62ms ✓ src/telegram/bot-message-context.dm-threads.test.ts (5 tests) 21ms Test Files 5 passed (5) Tests 81 passed (81) ``` ## Human Verification (required) - Verified scenarios: Type check, build, unit tests for all 3 channel modules (telegram, LINE, slack) - Edge cases checked: All 14 call sites continue to resolve the shared import; no re-export needed since consumers import directly - What you did **not** verify: Runtime behavior on live channels (import-only change — no logic change) ## Compatibility / Migration - Backward compatible? `Yes` - Config/env changes? `No` - Migration needed? `No` ## Failure Recovery (if this breaks) - How to disable/revert this change quickly: Revert this PR (4 commits) - Files/config to restore: `src/utils.ts`, `src/telegram/bot-access.ts`, `src/line/bot-access.ts`, `src/slack/monitor/channel-config.ts`, and 5 consumer files - Known bad symptoms reviewers should watch for: Import resolution errors at build time (would surface immediately in CI) ## Risks and Mitigations None — pure import refactor of an identical utility function. <!-- greptile_comment --> <h3>Greptile Summary</h3> Clean refactoring that extracts the `firstDefined<T>` utility function from three identical copies (in `src/telegram/bot-access.ts`, `src/line/bot-access.ts`, and `src/slack/monitor/channel-config.ts`) into a single shared definition in `src/utils.ts`. All 8 consumer files are updated to import from the shared location. - All three original implementations were functionally identical — the shared version adds only an explicit `T | undefined` return type annotation - All 14 call sites across telegram, LINE, and slack modules now import from `src/utils.ts` - No stale imports remain; no logic or behavioral changes - Channel-specific access-control functions (`normalizeAllowFrom`, `isSenderAllowed`) correctly remain in each channel's `bot-access.ts` - Well-structured as 4 incremental commits: extract → update telegram → update LINE → update slack <h3>Confidence Score: 5/5</h3> - This PR is safe to merge — it is a pure import refactor with no logic changes. - All three original `firstDefined` implementations were verified to be functionally identical. The shared version in `src/utils.ts` has the same logic with an added explicit return type. All 14 call sites and 8 consumer files correctly import from the new location. No stale imports or missing references exist. Tests pass. The change is entirely mechanical. - No files require special attention. _{Last reviewed commit: 9ccc43a} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->