M3: harden render and CLI failure surfaces (#669)

* M3: harden render and CLI failure surfaces

Make content truncation observable, reject unknown CLI options, expose deterministic render work counters, and scope render failures to exact requests. Refuse silently reduced whole-page export rasters while preserving tiled rendering, and add heavy-vector and CLI regression coverage.

Co-authored-by: Codex <noreply@openai.com>

* Render: remember a failed render by page and kind again

A key with scale and tag made every zoom level and tile a new key: a
pathological page tied up a worker for the watchdog limit per request
(exhausting worker replacements) and was re-parsed each time. The
repeated-parsing check asks for a new generation and scale again.

* Export: pages too large at the chosen dpi export at the most the renderer allows, and say so

#669 made every Exporter refuse oversized whole-page renders, which
reached File > Export to image, doc_export_* and OCR: at 600 dpi any page
side over 13.65 in (Legal, A3, Tabloid) failed instead of exporting. The
exporter clamps again; Exporter::dpi_used reports the resolution a page
is drawn at, which the Export dialog's message and doc_export_png's
lower_dpi list mention. A source with reject_oversize still refuses
(CLI render keeps its strict config).

* doc_export_images: describe lower_dpi

* Render: ContentTruncated is reported once per page; the hayro-interpret patch is recorded

Nested forms, Type 3 glyphs and patterns are interpreted again and each
reported the exhausted budget; pdfcraft-render now keeps one. The warning
is part of hayro-interpret patch (18) (the page content budget): marked
in the code and described in vendor/README.md.

* CLI render: print render warnings (skipped content) to stderr

* CLI: the option check refuses unknown options only; commands report missing values themselves

text's own --page parsing (and its test on main) says what a page value
must be; the generic "needs a value" pre-empted it.

---------

Co-authored-by: Codex <noreply@openai.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>

crates/render/src/raster/work_queue.rs

@@ -296,7 +296,16 @@ mod tests {
     }
 
     fn page(req: RenderRequest, bytes: usize) -> RenderedPage {
-        RenderedPage { request: req, width: 1, height: 1, rgba: Pixels::from(vec![0u32; bytes / 4]), error: None, text: None, millis: 0 }
+        RenderedPage {
+            request: req,
+            width: 1,
+            height: 1,
+            rgba: Pixels::from(vec![0u32; bytes / 4]),
+            error: None,
+            text: None,
+            warnings: Vec::new(),
+            millis: 0,
+        }
     }
 
     #[test]