Document submit formatting button state

docs/superpowers/specs/2026-06-14-submit-formatting-button-state-design.md

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+# Submit Formatting Button State
+
+## Goal
+
+Make the code submission button reflect the automatic formatting request that runs before submission.
+
+## Behavior
+
+- For Python3, C, and C++, the button displays `格式化中` while the formatting API request is pending.
+- During formatting, the button uses the existing loading icon and is disabled to prevent duplicate submissions.
+- After formatting succeeds, the existing submission flow continues and the button can display `正在提交`.
+- A formatting error stops submission and clears the formatting state before showing the existing warning.
+- A formatter server or network failure keeps the existing fallback behavior: clear the formatting state and submit the original code.
+- Languages without automatic formatting skip this state and submit directly.
+- Existing button labels and judging/cooldown behavior remain unchanged.
+
+## Implementation
+
+Add a component-local `isFormatting` ref in `SubmitCode.vue`.
+
+- Include it in `submitDisabled`.
+- Give it priority in `submitLabel`, using `格式化中`.
+- Include it in the loading-icon condition.
+- Set it immediately before `formatCode`.
+- Clear it in a `finally` block so every formatter outcome restores the button state.
+
+The state remains local because it is transient UI state owned only by the submission button.
+
+## Verification
+
+The frontend currently has no automated test suite. Verify with:
+
+- TypeScript production build.
+- Manual inspection of the state transitions for successful formatting, formatting errors, formatter infrastructure failures, and languages that do not format.