fix(cli): disable Freebuff chat logo sheen

[c8dhjp4tyv-bit]

Summary

• disable the animated chat-header logo sheen in Freebuff builds
• keep the existing animation for standard Codebuff builds
• add focused regression coverage for both product paths

Fixes #1035

Validation

• focused animation tests: 3 passed
• related queue tests: 4 passed
• full CLI suite: 2,367 passed, 9 skipped; existing checkout/environment failures remain (34 failed tests and 32 harness errors)
• CLI typecheck: existing missing tar and react-dom/server declarations; no errors from changed files
• Prettier check for changed files: passed
• git diff --check: passed

[codebuff-team]

Nice, minimal fix. The extraction of shouldAnimateChatHeader into its own pure function in cli/src/utils/chat-header-animation.ts is the right call — it's independently testable and keeps chat-header.tsx unchanged in structure (single line diff). Tests in chat-header-animation.test.ts cover the three meaningful branches (Freebuff-off, Codebuff-on, and inactive-in-either-case), which is proportionate to the size of the change.

A couple of things a maintainer will likely want confirmed before porting:

1. Confirm IS_FREEBUFF is genuinely a build-time/product flag already used elsewhere in cli/src/utils/constants.ts — the diff assumes it exists and is already threaded through chat-header.tsx, which it is per the import list, so this looks consistent with existing conventions rather than introducing a new product branch.
2. The linked issue (Can the FREEBUFF flashing effect displayed by CLI be turned off? It is currently causing the input method to flicker #1035) presumably describes the flicker/visual bug — worth double-checking the fix is actually disabling the right animation and not just papering over a timing bug in useSheenAnimation itself that could resurface elsewhere.

Overall this is a clean, scoped, well-tested change that should port cleanly by hand.

[c8dhjp4tyv-bit]

Verified both points against the current tree:

1. IS_FREEBUFF is the existing Freebuff build-time product flag in cli/src/utils/constants.ts; it is injected via --define/FREEBUFF_MODE and is already the flag imported by chat-header.tsx.
2. Issue Can the FREEBUFF flashing effect displayed by CLI be turned off? It is currently causing the input method to flicker #1035 is specifically about the flashing Freebuff logo causing input-method flicker, and its discussion explicitly asks to turn off the LOGO animation. This PR disables only the chat-header sheen for Freebuff while leaving Codebuff and inactive-header behavior unchanged.

So I don't see a broader useSheenAnimation timing bug that this change is masking; the scoped behavior matches the reported request.

[victorxheng]

Apologies — this PR was auto-closed by GitHub when we force-pushed a history rewrite of this repository (repository maintenance; every commit SHA changed). That was not a judgment on this PR, and GitHub does not allow us to reopen it because the commits it was based on no longer exist in the new history.

If you'd like to continue with this change: rebase your branch onto the new main (or recreate it from a fresh clone) and open a new PR — feel free to link back to this one for context, and we'll pick up the review there.

Sorry for the churn, and thanks for contributing.