[JBoggsy]

Let embedded replay viewers opt into native camera input

Depends on #102 (stacked on replay-control).

What and why

With embed=1 the viewer blocks all mouse, wheel and touch input so the host page can draw over it. Coaching hosts also want a "camera tool" mode where the game's own camera takes the pointer, including rotation, without leaving embed mode. This adds an opt-in switch for that.

• replay.html: a nativeCamera=1 URL option, polyworldReplay.setNativeCamera(on) and a nativeCamera postMessage command. While on, the capture-phase blocker lets pointer events through; key presses are still kept from the game and forwarded to the host. state().nativeCamera reports the current value. It only works with embed=1; non-embedded viewers already take input.
• GotA: embedded input goes through a new updateEmbeddedCamera: drag pans (the ground follows the pointer), right-drag orbits (sideways turns, up/down tilts), wheel or pinch zooms. It never selects units. A drag starts only on a press seen while input is enabled, so toggling the switch mid-drag can't leave a drag stuck.
• GotA had no camera rotation at all — its RTS camera is fixed-north. So this PR adds orbit angles: rtsCameraEye takes optional yaw/pitch (defaults unchanged), rtsDragPan pans relative to an orbited camera, and the GotA spectator pan uses it (identical at yaw 0). The director always resets to north.
• camera({mode: 'fixed', ...}) takes optional yaw and pitch in radians (NaN/omitted keeps the current angle), so a host can restore the default view with yaw: 0, pitch: 0.92. This changes the polyworld_replay_camera export signature (two extra floats); replay.html is the only caller.
• Embedded wheel zoom uses exp(-scroll * 0.002) instead of the native 0.92^(scroll/3): Chrome on macOS reports about 100 scroll steps per wheel notch, which with the native curve jumps straight to the closest zoom in one event.

What to look at

• examples/gods_of_the_arena/graphics.nim: the follow-selection tail of updateCamera moved unchanged into followSelectedCamera, so the embedded branch can return early and still follow. The embedded flag moved up so the camera closures can see it.
• Orbit gesture choice (right-drag) and the pitch range 0.35..1.45 rad in rtscameras.nim.
• A pan stops following a unit; an orbit or zoom keeps following it.

Tests

macOS arm64, Nim 2.2.10, Emscripten 6.0.12.

• nim r tests/test_rtscameras.nim (new orbit/pan cases), tests/test_replaycontrols.nim (camera angles, NaN keeps), tests/test_player.nim: pass.
• nim r tests/tests.nim: all tests passed; tests/test_directors.nim: pass (run on this branch merged with the two sibling PRs).
• nim check GotA desktop, -d:headless, -d:coworld: pass.
• test_browser_with_playwright.py --control-only --gpu: all checks pass, including the new native camera check (real mouse: blocked wheel does nothing; with the switch on, left-drag pans, right-drag turns the view matrix, wheel zooms, Space stays with the host, yaw: 0, pitch: 0.92 restores the north matrix exactly, and turning it off over postMessage blocks input again). Also passes on SwiftShader.
• Used downstream in PlayerADE's coaching Camera tool: an overlay drawing stays aligned to within 2e-5 px after a native rotation (headed Chromium, Metal).

Docs: docs/replay-control.md (URL option, gesture table, setNativeCamera, camera angles).

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