Productize automatic execution cadence in Goal settings

[huangruiteng]

Problem and behavior

The quota-owned automatic-execution minimum interval from #4921 had no Goal settings editor, so an operator could not inspect inheritance or safely change a Goal, Agent, or automation floor from the product. Goal-specific settings also did not identify which Goal was being edited.

This adds an Automatic execution interval settings panel with effective-floor provenance, scoped preview, revision-checked apply, and readback. The shared settings heading now names the active Goal on Goal-specific tabs and clears that label on machine-wide tabs. The loopback API delegates policy decisions and writes to the existing quota owner; it does not create a second scheduler policy. The RFC checkpoint is updated to reflect the delivered UI and remaining host-admission work.

The panel explicitly states that this is a scheduler recommendation: it does not mutate existing Codex App automation schedules, and App timer-to-pre-model-hook admission remains unqualified. Managed Turn admission is tracked separately in #4929.

Validation

• 83 focused Python tests covering real loopback HTTP, quota file-store readback, stale revisions, scope inheritance, and explicit reduction intent.
• Dashboard TypeScript check and packaged chat build passed.
• Development and packaged browser scenarios passed for preview/apply/readback, Goal identity across tabs, Agent inheritance, and desktop/mobile layout.
• Ruff lint/format and risk-based premerge passed; premerge selected 19 checks with no failures or manual holds. Public/private boundary scan passed.

Future-facing boundary pass: reused the existing Goal settings navigation and quota authority, removed duplicate readback metrics, and left App hook work outside this PR.