docs(ledger): record product decisions on upstream overlaps

[incognitojam]

Records the maintainer's decisions for four fork features where upstream now behaves differently, so the next intake and any agent touching these areas knows which way to go and why. Only .github/fork-features.yml changes.

Entry	Decision
pull-request-linked-extras	retiring. Take upstream's badge button and pull request tooltip (pingdotgg#13211 and the new orchestrator, pingdotgg#2829) and drop the fork's #102 +1 label and hover-card-only list.
server-restart-continuation-note	Keep. The new orchestrator continues a restarted thread with a visible "Continue where you left off." message that starts a new response. The fork keeps its small note inside the interrupted response, and at that intake web and mobile draw the new message as the note.
server-update-guidance	Keep waking threads whose background work was running when an in-app update restarted the server. pingdotgg#15604 leaves them asleep. A thread the user settles has nothing to wake, because settling stops its provider session.
workspace-thread-organization	Keep worktree as the default (the current checkout when the repository has no commit). Once pingdotgg#12954 is taken in, this becomes styal's built-in last step after t3.json and project settings.

Each decision goes into the entry's rationale or retire_when, where intake reads it when resolving a conflict. The three kept entries return to maintained.

Verification

vp run --filter @t3tools/scripts ledger:check validates all 89 entries, and the file is formatted.

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Written by an agent (Claude Code, claude-opus-5-5).