feat: make media inspection progressive

README.md

@@ -17,9 +17,9 @@ under Toolbox Portal with shared shell, theme, help and app switching.
 
 Two workflows keep the product intentionally smaller than a nonlinear editor:
 
-- **Quick Convert:** drop/import media, inspect streams, choose a
-  capability-checked preset/streams, convert, preview when the browser can, and
-  download.
+- **Quick Convert:** drop/import media, play it and read browser-native file
+  information immediately, then inspect streams on demand when an export needs
+  authoritative details.
 - **Edit:** a media bin and sequential non-overlapping clip timeline with
   non-destructive settings, one export at a time.
 
@@ -225,10 +225,12 @@ profile.
 
 `AV_TOOLS_LARGE_MEDIA=/absolute/video.mp4 npm run evidence:large-preview`
 performs the opt-in large-file regression: the native video element must mount
-and advance before bounded inspection finishes, remain the same element after
-the authoritative probe completes and produce no browser error.
+and advance while detailed inspection remains idle, browser-native
+duration/dimensions must appear without loading FFmpeg, and the same element
+must survive a subsequently requested authoritative probe. The command runs
+that evidence in both Chromium and Firefox.
 
-The latest recorded local Vitest run on 2026-07-26 completed **313 passing
+The latest recorded local Vitest run on 2026-07-27 completed **332 passing
 tests and two conditional skips**. It includes broad structured-command
 execution against native FFmpeg 7.1.3; the skipped native subtitle burn-in and
 labeled contact-sheet cases require `subtitles` and `drawtext` filters that are
@@ -241,9 +243,11 @@ queue and recovery workflows. The MT core is directly initialized and queried,
 and completes a real non-empty, re-probeable H.264/AAC conversion; the same
 path is benchmarked with 2-second 160×90 and 6-second 640×360 inputs. Nested
 static/Toolbox-context loading is also covered. This evidence is
-Chromium-specific: Firefox, Safari, mobile and exhaustive MT operation parity
-remain unrecorded. The exact one-run performance record and its limitations are
-in [performance observations](docs/PERFORMANCE.md).
+Chromium-specific. Firefox now covers the opt-in large-file
+play-before-inspection regression and its explicit authoritative-probe
+transition; broad Firefox operation parity, Safari, mobile and exhaustive MT
+operation parity remain unrecorded. The exact one-run performance record and
+its limitations are in [performance observations](docs/PERFORMANCE.md).
 
 ## Deployment