chore(.github): heal develop divergence + drop self fr-gate caller

[LukasWodka]

Summary

Two-in-one housekeeping for the now docs-treated .github:

1. Heals the squash divergence — develop was 1-ahead / 8-behind main (squash-merge artifact). This branch is cut from main, so merging it into develop (as a merge commit) brings develop up to main's history.
2. Drops fr-gate-caller.yml — .github has no deployable environment to functional-review on, so its self-gate was always red on its own main promotions. The reusable fr-gate.yml (called by every other repo) is untouched.

Follow-up PR promotes the caller removal develop→main.

Part of #1273 / RFC-0008 (.github docs-treatment).

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Note

Low Risk
Workflow-only changes: simpler labeling for customer issues and removal of a redundant gate on the .github repo, with no application runtime impact.

Overview
Customer-flagged issues no longer set the kanban Priority single-select via GraphQL. When from:customer is applied, the reusable customer-priority-bump workflow now runs gh issue edit to add the priority issue label (D5), matching the board’s move away from a Priority project field.

Removes .github/workflows/fr-gate-caller.yml, so this meta-repo no longer runs the FR gate on its own PRs. The shared reusable fr-gate.yml used by other repositories is unchanged.

^{Reviewed by Cursor Bugbot for commit 9850115. Bugbot is set up for automated code reviews on this repo. Configure here.}

[LukasWodka]

👋 Heads-up — Code review queue is at 38 / 30

Above the WIP limit. The team convention is to review existing PRs before opening new work.

Open PRs currently in Code review (oldest first):

• averaging-service#207 — Promote develop → staging · author: @shujaatTracebloc · no reviewer assigned
• backend#1201 — docs(rfc): Data spaces & federated dataset composition (draft) · author: @LukasWodka · no reviewer assigned
• backend#1217 — docs(rfc): Dataset integrity & score reproducibility (draft) · author: @LukasWodka · no reviewer assigned
• backend#1228 — Promote develop → staging · author: @shujaatTracebloc · reviewer: @saadqbal
• backend#1244 — fix(experiments): surface save-time failures as 5xx + guard new NOT NULL columns · author: @LukasWodka · reviewer: @saqlainsyed007
• backend#1251 — docs(bugbot): add .cursor/BUGBOT.md project context (#930) · author: @LukasWodka · no reviewer assigned
• backend#1254 — docs(pr-template): owner-qualify cross-repo closing keywords · author: @LukasWodka · no reviewer assigned
• backend#1259 — docs(rfc): qualified RFC identifiers + org-wide index · author: @LukasWodka · no reviewer assigned
• backend#1261 — RFC-BACKEND-0008: board & process reset (decision RFC — for markup) · author: @LukasWodka · no reviewer assigned
• cli#397 — Release develop → main · author: @shujaatTracebloc · no reviewer assigned

Pull from review before opening new work. (This is a nudge from the kanban WIP check, not a block.)