F-key scenes can be stored but not recalled (scene/view fallback missing from key dispatch)

[javierbq]

Summary

RayMol#258 wired up cmd.set_key dispatch, which made PyMOL's 125 built-in default bindings live for the first time. That surfaced an asymmetry in the F-key scene workflow: you can store a scene to an F-key but not recall it.

• CTRL-F1 … CTRL-F12 → scene F1, store … scene F12, store are real entries in modules/pymol/shortcut_dict.py (lines 112–137), so storing works.
• Bare F1 … F12 are not in the defaults. In upstream PyMOL, recall works anyway because _special falls through: it tries _invoke_key first, and if no binding exists it looks the key up against the scene list and the view dict.

RayMol's bridge calls pymol.internal._invoke_key(token) directly (PyMOLBridge_InvokeKey in PyMOLBridge.mm), deliberately bypassing _special — because PyMOL_Special also grabs arrows for the core's hidden Ortho prompt, which RayMol doesn't use. The side effect is that the scene/view fallback is skipped too.

Impact

A user presses ⌃F1 to store a scene, then presses F1 to get it back and nothing happens. Storing silently succeeds; recall silently does nothing. Scenes are still reachable via the Scene panel and the scene F1 command, so this is a parity gap rather than data loss.

Not a regression — before #258 neither half worked.

Proposed fix

Add an invoke(token) helper to modules/pymol/raymol_keys.py that mirrors _special's fallthrough without touching upstream files:

1. internal._invoke_key(token, 1) — if it fires, return true.
2. Otherwise, for special-key names only, try the scene list then the view dict, using the same Shortcut-based prefix interpretation _special uses.
3. Return whether anything fired.

Then point PyMOLBridge_InvokeKey at that helper instead of _invoke_key. The consume-iff-fired contract the monitor depends on is preserved: a successful scene recall counts as fired.

Keep it out of the arrow path — left/right are bound to movie frames by default, so they never reach a fallback anyway, and we do not want to reintroduce Ortho's arrow-grabbing behavior.

Verification

• Pure-Python test in testing/tests/test_raymol_keys.py: with a fake cmd exposing a scene list, assert invoke('F1') recalls the scene and returns true; assert an unknown token returns false.
• Manual: ⌃F1 to store, orbit away, F1 to recall.