Bump amy to 4885773 (amy main, 1.2.58 — includes merged amy#874)

amy#874 (bus-dsp-hook: the postprocess hook, js hooks v2 and the
external hook context API this branch depends on) has been merged
upstream, so the pin moves from the PR branch to amy main proper.
Also picks up 1.2.56-1.2.58: set_render_load_thresh and a
BSD-sed-safe constants.py regen. Vendored refdocs re-synced at the
new pin.

Browser-verified at this pin on the local web build: user C effect
and oscillator both live in the AMY worklet, no errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: bwhitman

amy

@@ -1,3 +1,3 @@
 Auto-generated by tulip/server/sync_amy_docs.py — do not edit by hand.
-Source: amy@5376e2fcddf44d972d48f2e9d736fdfa4389b497
+Source: amy@c6a9bf6101ee517174160b1eb2196973d92e3a8c
 Files: api.md, arduino.md, billie_jean.md, godot.md, juno_patches.md, midi.md, synth.md, upgrading.md