M10: the Verify screen downloads the web OCR models itself (ocr.ocr-web)

In the web build, Verify's Run OCR and its page/region re-reads never
started the model download. On a fresh page they failed at once with the
desktop's "set PDFCRAFT_MODELS" message, and worked only after Recognize
Text had downloaded the models.

Both now start the download (web_models_missing), say "Downloading the
text recognition models…" and remember what was asked; poll_models runs
it once the models land, or shows "Couldn't download the text
recognition models: {e}" when the download fails. Nothing runs if the
screen was closed meanwhile, and an engine the browser can never run
says why instead of waiting.

Tests: models_landed starts a waiting run and a waiting re-read, reports
a failed download without touching the review, and runs nothing for a
closed screen. The first three fail without the fix. Checked by hand in
Chrome: a fresh page, Verify > Run OCR downloads the models and reads
the page (47 words on a real scan); with the models missing it shows
the HTTP 404 and a second click after restoring them works.

parity/acrobat-features.toml

@@ -6947,8 +6947,8 @@ milestone = "M10"
 status = "shipped"
 commands = ["ocr.recognize"]
 tools = []
-evidence = ["crates/ocr/src/lib.rs::reads_rendered_text_with_models_from_bytes", "crates/ocr/src/lib.rs::models_from_bad_bytes_are_an_error", "crates/ocr/src/lib.rs::lines_survive_json", "crates/ocr/src/lib.rs::malformed_json_lines_are_an_error", "crates/engine/src/ocr.rs::an_installed_recognizer_is_available_and_handed_out", "crates/engine/src/ocr.rs::reading_page_by_page_matches_a_run", "crates/engine/src/tests.rs::reading_a_page_at_a_time_finds_the_same_words", "crates/ui-egui/src/workflows/ocr_ui.rs::a_scan_found_without_the_models_is_read_once_they_load", "xtask/src/web.rs::worker_files_get_content_hashed_names_that_point_at_each_other", "crates/ui-egui/src/workflows/ocr_route.rs::answers_go_to_the_run_that_sent_the_page_in_either_start_order", "crates/ui-egui/src/workflows/ocr_route.rs::a_cancelled_run_lets_the_other_and_the_next_run_finish"]
-notes = "The web zip carries the models in models/ beside index.html (packaging/web/package.sh); Recognize Text downloads them on first use (about 12 MB, with a spinner, an error and a retry button). Pages are rendered on the page and read in Web Workers (apps/pdfcraft-ocr-worker; up to two, one core left to the page; idle workers close after a minute), so the page keeps responding; where workers can't start the page reads them itself. Recognize Text and Recognize Text in Multiple Files can run at once: each worker's answer goes back to the run that sent the page (crates/ui-egui/src/workflows/ocr_route.rs). Checked by hand in a browser on a 4-page synthetic scan (2026-10-12). Built with WebAssembly SIMD (2.4× faster than scalar in wasmtime). The page renders, crops and cleans each page (the #977 options) and only the engine runs in a worker, so a cleaning step slows the page while it runs; ocrs only (no Tesseract on the web), and the Verify screen re-reads a page or region on the page itself. Missing: no automated browser test yet; a wasm page reads about 17× slower than native; each worker holds about 600 MB while reading; no download progress or offline cache beyond the browser's HTTP cache."
+evidence = ["crates/ocr/src/lib.rs::reads_rendered_text_with_models_from_bytes", "crates/ocr/src/lib.rs::models_from_bad_bytes_are_an_error", "crates/ocr/src/lib.rs::lines_survive_json", "crates/ocr/src/lib.rs::malformed_json_lines_are_an_error", "crates/engine/src/ocr.rs::an_installed_recognizer_is_available_and_handed_out", "crates/engine/src/ocr.rs::reading_page_by_page_matches_a_run", "crates/ui-egui/src/workflows/ocr_verify.rs::a_run_that_waited_for_the_models_starts_when_they_land", "crates/ui-egui/src/workflows/ocr_verify.rs::a_failed_model_download_is_said_and_nothing_runs", "crates/engine/src/tests.rs::reading_a_page_at_a_time_finds_the_same_words", "crates/ui-egui/src/workflows/ocr_ui.rs::a_scan_found_without_the_models_is_read_once_they_load", "xtask/src/web.rs::worker_files_get_content_hashed_names_that_point_at_each_other", "crates/ui-egui/src/workflows/ocr_route.rs::answers_go_to_the_run_that_sent_the_page_in_either_start_order", "crates/ui-egui/src/workflows/ocr_route.rs::a_cancelled_run_lets_the_other_and_the_next_run_finish"]
+notes = "The web zip carries the models in models/ beside index.html (packaging/web/package.sh); Recognize Text downloads them on first use (about 12 MB, with a spinner, an error and a retry button); the Verify screen starts the same download and runs once it lands. Pages are rendered on the page and read in Web Workers (apps/pdfcraft-ocr-worker; up to two, one core left to the page; idle workers close after a minute), so the page keeps responding; where workers can't start the page reads them itself. Recognize Text and Recognize Text in Multiple Files can run at once: each worker's answer goes back to the run that sent the page (crates/ui-egui/src/workflows/ocr_route.rs). Checked by hand in a browser on a 4-page synthetic scan (2026-10-12), and after the port onto #977 on synthetic and real scanner scans, with word counts matching desktop (2026-11-07). Built with WebAssembly SIMD (2.4× faster than scalar in wasmtime). The page renders, crops and cleans each page (the #977 options) and only the engine runs in a worker, so a cleaning step slows the page while it runs; ocrs only (no Tesseract on the web), and the Verify screen's Run OCR and its page or region re-reads read on the page itself, not in a worker. Missing: no automated browser test yet; a wasm page reads about 17× slower than native; each worker holds about 600 MB while reading; no download progress or offline cache beyond the browser's HTTP cache."
 
 [[feature]]
 id = "ocr.scanner-acquire"