docs(linux): align the two guides on what Linux actually captures

Two claims went stale when evdev click capture landed, and they disagreed with
each other across the two public guides.

README said "click effects remain macOS and Windows only". That was true of the
portal, which still reports no mouse button events, but no longer true of the
app: the capture helper reads the left button from evdev instead. Rewritten to
say so, with the condition that actually matters to a user — the `input` group —
and what happens without it (recording unaffected, every sample a move).

website/docs/installation.md called the Linux capture pipeline "Browser
pipeline" while README described native PipeWire capture with a browser
fallback. The README was right: startNativeLinuxRecordingIfAvailable takes the
native path and only returns false on a missing helper, where the comment reads
"Falling back beats refusing to record". The table now says the same thing, and
names what the fallback costs.

Verified against the source rather than the docs — input.rs (left button only,
`input` group, OPENSCREEN_DISABLE_CLICK_CAPTURE), pipeWireCursorRecordingSession
and the Linux branch of useScreenRecorder — since writing a capability claim we
cannot keep is the defect this PR exists to fix.

Neither line was introduced here; both arrived on main with the Linux click
work. Corrected here rather than left to drift because this PR already touches
both files' macOS rows.

Author: EtienneLescot

README.md

@@ -171,7 +171,7 @@ You may need to grant screen recording permissions depending on your desktop env
 Everything in the editor and export is the same on macOS, Windows, and Linux: zooms, backgrounds, motion blur, crop/trim/speed, blur regions, annotations, auto-captions, AI editing, projects, export, and all languages. All three now record through a native capture pipeline; the remaining differences are narrower than they used to be:
 
 - **Native recording**: macOS (ScreenCaptureKit), Windows (Windows Graphics Capture), and Linux (PipeWire via the ScreenCast portal) all record through a native pipeline for higher quality and clean window-level capture. On Linux the browser pipeline stays as an automatic fallback if the helper isn't available.
-- **Custom cursors**: on macOS and Windows the real cursor is captured with shape, type, and clicks. Linux captures position and cursor shape through the portal, so cursor themes and the editable cursor overlay work there too — but the portal reports no mouse button events, so **click effects remain macOS and Windows only**.
+- **Custom cursors**: on macOS and Windows the real cursor is captured with shape, type, and clicks. Linux captures position and cursor shape through the portal, so cursor themes and the editable cursor overlay work there too. Click effects work on Linux as well, but not through the portal — Wayland exposes no portal for mouse buttons, so the capture helper reads the left button from evdev, which needs your user in the `input` group. Without that, recording is unaffected and every cursor sample is simply a move.
 - **Webcam**: Windows muxes the webcam natively into the recording; macOS and Linux record it alongside as a separate file. It works as a picture-in-picture overlay on all three.
 - **System audio** support varies by OS:
   - **macOS**: works on every supported version. On macOS 14.2+ you'll be prompted to grant audio capture permission.

website/docs/installation.md

@@ -131,7 +131,7 @@ The editing tools are the same everywhere — zooms, backgrounds, crop/trim/spee
 
 | | macOS | Windows | Linux |
 |---|---|---|---|
-| Capture pipeline | Native (ScreenCaptureKit) | Native (Windows Graphics Capture) | Browser pipeline |
+| Capture pipeline | Native (ScreenCaptureKit) | Native (Windows Graphics Capture) | Native (PipeWire via the ScreenCast portal); browser fallback without the helper, losing hardware encode and cursor telemetry |
 | Custom cursor themes / click effects | ✅ | ✅ | ✅ on Wayland — click capture needs the `input` group ([details](#mouse-clicks-on-wayland)) |
 | Webcam | Native capture | Native capture | Browser capture (still works as PiP) |
 | System audio | Works out of the box; permission prompt on macOS 14.2+ | Works out of the box | Needs PipeWire (default on Ubuntu 22.04+, Fedora 34+) |