Avoid duplicate verification when a draft becomes ready

[numinousmuses]

Opening a draft PR already starts Forge verification. Marking that same commit ready for review was starting a second full run with no code change. Remove that redundant trigger; opening, synchronizing, and reopening a PR still trigger verification.

This was observed on the prompted-work demo. The redundant queued run was cancelled before it allocated a Forge task.

Validation: regenerated the workflow from the platform template, reviewed the one-line diff, and ran all 14 bridge/workflow tests. This PR also passes through the fork's real Forge CI before merge.

Before:

flowchart LR
  D[Draft PR opened] --> O[forge-ci.yml opened event]
  O --> V1[run_ci.py submits Forge verification]
  R[Mark same draft ready] --> E[ready_for_review event]
  E --> V2[Duplicate verification of unchanged code]

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After:

flowchart LR
  D[PR opened or updated] --> O[forge-ci.yml opened or synchronize event]
  O --> V[run_ci.py submits Forge verification]
  R[Mark unchanged draft ready] --> Keep[Existing verified status retained]

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