Add scrolling capture of the window under the cursor

[x1xhlol]

Summary

Adds scrolling capture: a new hotkey action ("Scrolling capture of window under cursor", unbound by default) that captures an entire scrollable window — not just the visible part — by scrolling it and stitching the frames into one tall screenshot, saved as a normal Cap screenshot project.

How it works (scrolling_capture.rs):

capture window frame
loop (≤60 steps, ≤16000px):
    inject 2 wheel notches at the cursor (SendInput on Windows,
    CGEventCreateScrollWheelEvent2 on macOS) → wait 600ms for
    smooth-scroll to settle → capture next frame
    → detect vertical offset: minimal mean-absolute-difference over
      overlapping rows (top 20% skipped for sticky headers, ≥25%
      overlap required, 1px granularity)
    → offset == 0 (bottom reached) or no match → stop
    → append the frame's new bottom rows to the stitched image

• The hotkey targets the window under the cursor (same pattern as the existing "Screenshot current window" action), so the injected wheel events reach the right window.
• The stitched image goes through the normal screenshot-project save path: same toast, automations, editor-open behavior, library entry.
• No new dependencies; the stitching is a few dozen lines over image buffers.
• Known cosmetic limitation: sticky side columns (e.g. Wikipedia's TOC panel) repeat down the image — only top-anchored sticky content is compensated.

Showcase

A 60-section page captured into one 1280x7404 image:

Bottom of the stitch — capture stops at the page footer with no repeated content:

Testing (Windows, end-to-end on a live dev build)

Test	Result
60-section long page → 1280x7404 stitch, all sections in order, zero seam artifacts	✅
Stops at page bottom (footer present, nothing repeated)	✅
Wikipedia article → 1280x12680 continuous stitch (hit the 60-frame cap on a very long article)	✅
Non-scrolling window → single frame in ~5s, no hang	✅
Toast + normal .cap screenshot project on every run	✅
Regression: normal screenshot flow unaffected	✅

macOS compiles the same capture/stitch path with a CoreGraphics scroll-event injector; runtime-tested on Windows only.

Builds on #2095 (OCR text capture — shares its capture/save helpers); the scrolling-capture change itself is the top two commits.

Greptile Summary

This PR adds window scrolling capture, OCR area capture, associated hotkeys and settings, and refactors screenshot capture/saving into reusable backend helpers.

• Adds platform-specific synthetic scrolling and frame stitching for whole-window screenshots.
• Adds OCR selection, clipboard, notification, and optional screenshot-preservation flows.
• Extends persisted settings, hotkey actions, target-selection UI, window handling, and Tauri IPC bindings.

Confidence Score: 3/5

The PR should not merge until scrolling captures are capped before appending oversized strips and the Linux action is either implemented or disabled.

Near-limit captures can produce images rejected by the screenshot editor, while Linux exposes an action whose scroll injector performs no operation and therefore cannot capture off-screen content.

Files Needing Attention: apps/desktop/src-tauri/src/scrolling_capture.rs, apps/desktop/src/routes/(window-chrome)/settings/hotkeys.tsx, apps/desktop/src/utils/tauri.ts

Important Files Changed

Filename	Overview
apps/desktop/src-tauri/src/scrolling_capture.rs	Implements scrolling and stitching, but can exceed the image-height cap and silently degenerates to a single-frame capture on Linux.
apps/desktop/src-tauri/src/hotkeys.rs	Adds OCR and scrolling-capture actions plus default OCR hotkey seeding; the scrolling action reaches the unsupported Linux implementation.
apps/desktop/src-tauri/src/recording.rs	Refactors image capture and project saving and adds OCR capture while preserving the existing asynchronous PNG-save behavior.
apps/desktop/src/routes/target-select-overlay.tsx	Adds OCR area-selection capture and explicit success/error overlay lifecycle handling.
apps/desktop/src/utils/tauri.ts	Updates generated IPC bindings, contrary to the repository rule prohibiting direct changes to generated tauri.ts files.
apps/desktop/src-tauri/src/general_settings.rs	Adds backward-compatible defaulted OCR preferences.
apps/desktop/src-tauri/src/lib.rs	Correctly registers the new commands and scrolling-capture module.

Prompt To Fix All With AI

### Issue 1
apps/desktop/src-tauri/src/scrolling_capture.rs:74-83
**Height cap checked too late**

When a capture is near 16,000 pixels, the full next strip is appended before the cap is checked, allowing the result to exceed the screenshot editor's 16,384-pixel limit and fail to open.

```suggestion
        let remaining_height = MAX_STITCHED_HEIGHT.saturating_sub(stitched_height);
        let new_rows = offset.min(frame_height).min(remaining_height);
        if new_rows == 0 {
            debug!("Stitched image reached the height cap; stopping");
            break;
        }

        let strip = frame.crop_imm(0, frame_height - new_rows, frame_width, new_rows);
        stitched.push(strip);
        stitched_height += new_rows;
        prev = cur;

        if stitched_height >= MAX_STITCHED_HEIGHT {
            debug!("Stitched image reached the height cap; stopping");
            break;
        }
```

### Issue 2
apps/desktop/src-tauri/src/scrolling_capture.rs:158-187
**Linux scroll injection is absent**

When a Linux user invokes the exposed scrolling-capture hotkey, `inject_scroll` performs no operation, so the loop waits once and saves only the initially visible frame instead of capturing off-screen content.

### Issue 3
apps/desktop/src/utils/tauri.ts:59-70
**Generated bindings changed directly**

This directly modifies the generated `tauri.ts` IPC surface and includes unrelated generated type churn. These changes can be overwritten during regeneration and leave the checked-in bindings out of sync; regenerate the file from the Rust command definitions instead.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "Tune scrolling capture stepping and matc..." | Re-trigger Greptile}

Greptile also left 3 inline comments on this PR.

Context used (3)

• Context used - AGENTS.md (source)
• Knowledge Base — Desktop Tauri App (Rust Backend)
• Knowledge Base — Desktop Frontend (apps/desktop/src)