I2V Start/End frame-slot selectors still text-based (locale-agnostic follow-up to #24) #63

Summary

Spun off from #24 (which is being closed as the umbrella-task scope is otherwise complete). svasakorn flagged this in PR #60's body as scope-keeping:

FRAME_SLOT_BY_LABEL (I2V Start/End slots, div[aria-haspopup='dialog']:has-text('{label}')) is still text-based and will hit the same locale issue on a non-English profile. It's the I2V frame-slot path, separate from this upload fix, and belongs with #24.

Current code

src/gflow_cli/api/transports/ui_automation_video.py:138:

FRAME_SLOT_BY_LABEL = "div[aria-haspopup='dialog']:has-text('{label}')"

Used at line 633 in the I2V Start/End frame-slot binding path. Same root cause as #56: localized text matching (Flow's editor renders labels in the Chrome profile language, not the --lang=en-US Chromium launch arg).

Impact

gflow video i2v on a non-English Chrome profile would hit a silent hang ~38s in (the click-then-no-event signature) when trying to bind a Start or End frame. Same failure mode as PR #60 resolved for _attach_references in i2i.

Suggested fix shape (mirror PR #60)

1. Investigate the DOM on the affected profile via scripts/dev/capture_image_add_media_dom.py (or a sibling script for the video editor). Need to see whether the Start/End frame slot has a Material Symbols icon ligature (e.g. play_arrow for Start, stop for End, or similar). If yes → use button:has(i.google-symbols:text-is('<ligature>')). If no → structural disambiguation by panel position.
2. Replace FRAME_SLOT_BY_LABEL with a locale-stable selector or a cascade (icon-first, English-text fallback with short per-tier timeouts so two misses can't recreate a long silent hang — same pattern as PR fix(image): re-introduce i2i ref-attach (#50) with locale-agnostic media-dialog selectors (#56) #60).
3. Fail-loud if both tiers miss: screenshot + RuntimeError with the explicit "Chrome profile language vs Google account language" hint (PR fix(image): re-introduce i2i ref-attach (#50) with locale-agnostic media-dialog selectors (#56) #60's error message is the model).

Test plan (mirror PR #61)

• New e2e variant test_e2e_i2v_start_end_frame_attach in tests/e2e/test_transports_e2e.py, GFLOW_CLI_E2E_PROFILE-gated, ui_automation transport ONLY (REST transports drop UI-only fields silently — see rest-transports-drop-ui-fields memory).
• Assert on a structlog event that ONLY fires when the UI path executed (e.g. start_frame_attached / end_frame_attached if those exist; or add new ones).
• Verify on a non-EN profile (ffroliva) and an EN profile (svasakorn's setup).

References

• Make UiAutomationTransport selectors language-agnostic (structural-first) #24 — umbrella issue (closed; this is the last remaining selector)
• i2i ref attach (#50) fails with TimeoutError on ffroliva account; image-mode add-media flow likely differs from video R2V #56 — sibling i2i locale leak (resolved via fix(image): re-introduce i2i ref-attach (#50) with locale-agnostic media-dialog selectors (#56) #60 + fix(test): i2i e2e routed through REST (follow-up to #60) #61)
• fix(image): re-introduce i2i ref-attach (#50) with locale-agnostic media-dialog selectors (#56) #60 — production fix for i2i media dialog (_attach_references)
• fix(test): i2i e2e routed through REST (follow-up to #60) #61 — test fix + reference_attached assertion strengthen
• feat: locale-overridable Playwright launch (issue #24 prep) #51 — locale-agnostic phase 1 (env override GFLOW_CLI_LOCALE)
• Memory: flow-locale-leak-icon-ligatures — durable selector pattern across the codebase