tools: an agent's commands and tapes are credited to its connection

[foxnne]

Update 2026-10-18: main moved to Zig 0.17 and SDK 0.2.30 (#23), and that is merged in here; the repin below is now main's. What this PR adds is crediting the agent's steps.

Part of fizzyedit/plans#8

What changes

fizzy_act and fizzy_run gain a stroke step, so an agent can draw through a plugin's own tools (press, carry, release) and look at the result before its next mark:

{"stroke": {"tag": "pixi.canvas:/p/a.pixi", "ms": 60, "points": [
  {"fx": 0.39, "fy": 0.20}, {"fx": 0.33, "fy": 0.20, "ms": 70}]}}

• tag on the stroke is every point's that names none; each point's ms is the pen's time from the last.
• Any point (click, move, stroke) can now be given as fractions of its tagged widget, fx/fy, then nudged by x/y. With pixi's pixi.canvas:<path> anchor (the whole image's rect), pixel (x, y) of a w×h sprite is ((x + .5) / w, (y + .5) / h).
• The bridge's tool descriptions say so.

Needs fizzyedit/fizzy#431 (Script.stroke), so this builds only with --fork=<fizzy>/sdk until the next SDK release. Draft until then.

Verified

• macOS: built with --fork against that change into a sandbox profile; drew a 32×32 sprite in pixi with strokes (outline, box-select-and-delete, bucket fills, shading), checking each pass with pixi.read and fizzy_capture. zig fmt --check.

Found on the way (not fixed here)

• pixi.setTool {"tool": "pencil"} fails with "expected enum literal" even through fizzy_call.

🤖 Generated with Claude Code

[foxnne]

Seen live on macOS: fizzy main (0.2.29) under a sandbox profile, with this branch's agent, chat (fizzyedit/chat#15) and pixi (fizzyedit/pixi#48) installed. An MCP client that named itself claude-code in initialize called text.write through the bridge on an open note.txt; the pane's activity bubble read "Claude · Write Text", so the client's name reached hello and the step was the connection's.