M10: print from the web build through the browser's print dialog (gap 4) (#1243)

* Gates: fix two clippy failures on main

- ocr_ui: "Also recognize pages that already have text" used egui's own
  checkbox, which clippy.toml disallows (#1184 landed beside #1173);
  use widgets::checkbox like every other box.
- camera_edges: Rust 1.97's manual_range_contains; the rewrite keeps the
  old answer for a NaN angle (false) with an is_finite check.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_019ojKsSCHWk2AuyDTFMHCd7

* M10: print from the web build through the browser's print dialog (gap 4)

The web build had no printer: spool::submit refuses on wasm, so Print
could only download the print-ready PDF. Now its Print dialog offers
"Browser's print dialog" (the default there), which reaches every
printer the operating system knows.

- web_print: PdfCraft draws the print-ready PDF's sheets itself
  (engine Exporter), one sheet a frame since wasm has no threads:
  300 dpi up to 100 sheets, 200 up to 300, 150 up to 1,000, at most
  64 MP a sheet and 1 GiB of PNGs a job. The PNGs become blob URLs
  and print from a hidden srcdoc iframe, one sheet per page, margin 0.
- Chromium prints every page at the default @page size, so a sheet of
  the paper's size turned sideways is rotated 90 degrees CCW onto it
  (as drivers do); other sizes get named @page rules.
- Copies, two-sided and colour are greyed out (the browser's dialog
  sets them). If print() is refused (e.g. a sandboxed frame), the
  print-ready PDF downloads instead, with the reason.
- pdfcraft-print stays free of web APIs; six new strings in all 20
  catalogs (ATTRIBUTION hashes refreshed); docs and parity updated,
  gap 4 closed.

Verified in headless Chromium against a trunk build: three sheets at
300 dpi, the landscape sheet turned, no blank trailing page, and the
download fallback. Firefox and Safari not yet tried.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_019ojKsSCHWk2AuyDTFMHCd7

---------

Co-authored-by: Claude <[email protected]>
Co-authored-by: Brandon Thomas <[email protected]>

docs/gaps.md

@@ -1,6 +1,6 @@
 # Where PdfCraft falls short of Acrobat Pro
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-12 · **Change:** exclusive image-crop resize follow-up; minor (Word invoice regression coverage, #773; Office fidelity still partial; gap 2: hayro patch counts after the native-gradient backport) · **Target:** Adobe Acrobat Pro (Acrobat DC, continuous track 26.002.21931, macOS)
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-12 · **Change:** gap 4 closed: the web build prints through the browser's print dialog; exclusive image-crop resize follow-up; minor (Word invoice regression coverage, #773; Office fidelity still partial; gap 2: hayro patch counts after the native-gradient backport) · **Target:** Adobe Acrobat Pro (Acrobat DC, continuous track 26.002.21931, macOS)
 > **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-12 · **Change:** minor (gap 13: large-file memory measured, edits keep two copies instead of three, file-backed input blocked on gap 2) · **Target:** Adobe Acrobat Pro (Acrobat DC, continuous track 26.002.21931, macOS)
 > **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-11 · **Change:** minor (gap 1 closed by #836; fixed issues removed from gaps 3, 6 and 16) · **Target:** Adobe Acrobat Pro (Acrobat DC, continuous track 26.002.21931, macOS)
 > **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-11 · **Change:** minor (document-font subset completion and curved/shared image clips in the contributor fork; gap 2: hayro patch counts after the native-gradient backport) · **Target:** Adobe Acrobat Pro (Acrobat DC, continuous track 26.002.21931, macOS)
@@ -13,7 +13,8 @@ feature lacks).
 
 No gap blocks the [alpha gate](roadmap.md#alpha-gate); gap 8 holds the convert-and-share
 workflow's partial sub-cases and is the first beta item. Gap numbers are kept when a gap closes, so
-references elsewhere stay valid (gap 1, encrypted output Acrobat rejected, closed with #836).
+references elsewhere stay valid (gap 1, encrypted output Acrobat rejected, closed with #836; gap 4,
+no printing on the web, closed by printing through the browser's print dialog).
 
 Hours are Opus 5.5 agent wall-clock hours. "Doc" names the parity document the gap belongs to.
 When a gap closes, delete its entry, note it in the [ROADMAP.md](../ROADMAP.md) progress log and
@@ -25,7 +26,6 @@ update the numbers.
 |---|---|---|---|---|
 | 2 | Rendering is borrowed and its fidelity unmeasured | feature, spec | 110–190 | [pdf-spec-parity.md](pdf-spec-parity.md) |
 | 3 | Editing existing text is fragile on real files | feature | 100–180 | [target-app-parity.md](target-app-parity.md) |
-| 4 | No printing on the web | feature, platform | 15–30 | [hardware-parity.md](hardware-parity.md) |
 | 5 | Chinese UI shows missing-glyph boxes in releases | localization | 6–12 | [localization-parity.md](localization-parity.md) |
 | 6 | Open-issue backlog of wrong results in shipped features | stability | 45–80 | this file |
 | 7 | OCR reads only unaccented Latin | feature | 40–75 | [file-format-parity.md](file-format-parity.md) |
@@ -104,16 +104,6 @@ update the numbers.
   how a document looks.
 - **Estimate:** 100–180 h (the longest feature pole, M7). **Doc:** [target-app-parity.md](target-app-parity.md).
 
-### 4. No printing on the web
-
-- **Missing:** browser printing.
-- **Evidence:** the web build has no spooler: off Windows and unix, `spool::submit` reports that
-  printing to a printer isn't available and only the print-ready PDF can be saved.
-  `crates/print/README.md`: "Not yet: the web spooler".
-- **Impact:** the web build cannot send a job to a printer; printing is a P0 workflow. Printing on
-  Windows shipped with [#756](https://github.com/storytold/pdfcraft/issues/756).
-- **Estimate:** 15–30 h. **Doc:** [hardware-parity.md](hardware-parity.md).
-
 ### 5. Chinese UI shows missing-glyph boxes in releases
 
 - **Missing:** a Simplified Chinese (`Hans`) UI face in release builds and a working fallback.
@@ -322,6 +312,7 @@ update the numbers.
 |---|---|---|
 | 2026-10-12 | minor | Exclusive image crops resize with their pixels across nested states, intervening operators and content streams; shared clips remain fixed. Synthetic engine/tool regressions and private image save/reopen checks; estimates unchanged. |
 | 2026-10-12 | minor | Gap 13: measured large-file memory; edits no longer keep the previous working file while writing the next (peak 3 → 2 copies); file-backed input recorded as blocked on gap 2 |
+| 2026-10-11 | minor | Closed gap 4: the web build prints through the browser's print dialog (sheets drawn by PdfCraft at 150–300 dpi, one per printed page); number kept |
 | 2026-10-11 | minor | Word invoice failure #773 has synthetic regression coverage; broader Office conversion remains gap 8. |
 | 2026-10-11 | minor | Contributor fork: mixed-style visual regions, source-font space reuse and a read-only textless background. Embedded sfnt source faces and Mac subset Unicode mappings keep edit baselines stable; live frames follow Apply/Save geometry as text grows or shrinks. Engine/tool/UI regressions and private all-page checks cover the changes; full matching font import, CFF, range styles, shaping and private Chinese typing checks added; legacy programs and general fidelity remain open; estimates unchanged |
 | 2026-10-11 | patch | Gap 2: 23 hayro-interpret and 10 hayro patches after axial and radial shadings became native gradients (backport of hayro 0.8) |