refactor(router): extract shared credential resolution helpers

[aaight]

Summary

• Creates src/router/credentials.ts with three shared helpers: resolveTrelloCredentials(), resolveJiraCredentials(), and buildGitHubHeaders()
• Refactors acknowledgments.ts, reactions.ts, notifications.ts, and pre-actions.ts to use these helpers, eliminating ~300 LOC of duplication
• Adds tests/unit/router/credentials.test.ts with 12 unit tests covering success + failure paths for all helpers

Details

Before: Trello credential resolution (2 getIntegrationCredential calls + try/catch) was duplicated 5×; JIRA credential resolution (3 calls + findProjectById + base64 auth) was duplicated 5×; GitHub API headers object was duplicated 7× across 4 files.

After: Single call to the appropriate helper returns typed credentials or null on failure.

Zero behavior change — all 191 existing router tests continue to pass. The 6 pre-existing failures in config/projects.test.ts are unrelated to this PR.

Test plan

• All 191 existing router tests pass
• 12 new credentials.test.ts tests pass (success + failure paths)
• npm run typecheck — zero errors
• npm run lint:fix — zero errors (one pre-existing warning in unrelated file)

Card: https://trello.com/c/699b695aa4474a69ca67a7b9

🤖 Generated with Claude Code

[zbigniewsobiecki]

@aaight resolve conflicts

[aaight]

Request Addressed

What was asked

Resolve merge conflicts on the PR branch.

Changes Made

• Rebased feature/router-credential-helpers onto dev
• Resolved conflicts in 4 files (acknowledgments.ts, notifications.ts, pre-actions.ts, reactions.ts) by accepting dev's versions
• Removed redundant credentials.ts and credentials.test.ts — superseded by platformClients.ts from PR refactor(router): extract shared credential resolution & platform API helpers #492 which landed the same refactoring

Verification

• All 205 router tests passing
• All 2645 non-config tests passing (6 pre-existing failures in config/projects.test.ts are unrelated)
• Typecheck passing

Note

This PR's changes were fully subsumed by PR #492. The branch is now at 0 commits ahead of dev, so this PR can likely be closed.

[aaight]

Conflicts resolved! I rebased the branch onto dev.

The conflicts were caused by PR #492 (refactor/router-platform-clients) which landed on dev with essentially the same refactoring — extracting shared credential helpers into platformClients.ts (this PR used credentials.ts). Since dev already has the complete refactoring:

• Rebased onto dev, accepted dev's versions for all 4 conflicting files (acknowledgments.ts, notifications.ts, pre-actions.ts, reactions.ts)
• Removed the now-redundant credentials.ts and credentials.test.ts (superseded by platformClients.ts and platformClients.test.ts from refactor(router): extract shared credential resolution & platform API helpers #492)
• All 205 router tests pass, typecheck clean

Note: This PR's commit was entirely subsumed by #492, so the branch now has 0 commits ahead of dev. You may want to close this PR since the refactoring has already been merged.