tweetButton / Ctrl+Enter: debounce / single-flight to prevent twin posts

[Trace824]

Summary

A single automation click on the inline tweet/reply button (or equivalent Ctrl+Enter) has been observed to fire twice, producing twin posts. Send should be single-flight / debounced.

Repro

• Context: Compose ready; click [data-testid=tweetButtonInline] (or reply tweetButton) via FSB click tools.
• Steps:
  1. Issue one click (or one Ctrl+Enter press_key).
  2. Observe network/UI for duplicate post creation.
• Observed: occasional twin posts from one logical send.

Code pointers (verified against /workspace/FSB)

• extension/site-guides/social/twitter.js — tweetButtonInline, tweetButton (~L47, ~L139–141).
• extension/content/actions.js — click tool path; no send-specific single-flight found (likely area to add).
• Existing debounce utilities elsewhere (e.g. extension/content/visual-feedback.js) are for overlay text, not tweet send.

Proposed fix

Wrap tweet/reply send clicks (and Ctrl+Enter on compose) in a short single-flight lock per tab so a second dispatch within N ms is ignored or coalesced.

Acceptance / regression

• Double-dispatched click → one post.
• Intentional second post after unlock still works.

Owner

extension

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Priority: P2 · Owner: extension