amyboard: add Display.hline/vline and document the display drawing API

[bwhitman]

What

• Add hline(x, y, w, col) and vline(x, y, h, col) to the Display class in amyboard.py, as thin forwards to the underlying framebuf (which supports them natively) — matching the existing line/rect/fill_rect primitives.
• Enumerate the full set of Display drawing methods in the sketch-generator system prompt (amyboardworld_db_api.py) so the model only uses methods that actually exist.

Why

The sketch generator AI naturally reaches for display.hline(...), which the Display class did not expose, producing a runtime crash:

AttributeError: 'Display' object has no attribute 'hline'

hline/vline are trivial framebuf forwards, so implementing them is more robust than telling the model to avoid them. The expanded prompt guidance lists the exact drawing API surface (fill, fill_rect, rect, line, hline, vline, pixel, text, scroll) and notes there is no circle/ellipse/print, so the model stops inventing methods.

Rollout notes

• The amyboard.py change ships in firmware — it takes effect once an AMYboard is reflashed/upgraded.
• The prompt change takes effect on the next Railway deploy (auto on push to main) and immediately stops the generator from emitting unsupported calls, covering older firmware too.

🤖 Generated with Claude Code

[github-actions]

🔌 AMYboard PR preview

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[github-actions]

🌷 Tulip Web PR preview

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Flash a Tulip to this build: on-device run tulip.upgrade(pr=1062).

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[github-actions]

🎛️ HW CI (physical bench)

AMYboard (USB-MIDI + AMY zP → audio): ✅ PASS — flashed this PR’s firmware; all checks matched the references.

Tulip (TULIP4_R11; serial-REPL audio + WiFi screenshot): ✅ PASS — flashed this PR’s firmware; all checks matched the references.

⬇️ Artifacts: recordings · screenshot · serial logs · run logs

_{Self-hosted bench. Audio spectral-compared to ref/hwci_basic.wav + ref/tulip_basic.wav; Tulip screenshot pixel-compared to ref/tulip_screenshot.png. Both analog outs share one capture card, so the tests run sequentially.}