docs: bring the documentation up to the shipped surface

[derfsss]

Documentation-only. No code, no version change.

A full pass over the README and everything it links to, checking each document against what the code actually does rather than against itself. Verified mechanically: all 137 live tools and 59 daemon methods appear in COMMANDS.md, and every internal link and anchor across the 13 documents resolves.

Gaps closed

Ordered by what they'd cost a user:

• z.library was never listed as a target requirement, although fs.upload compression and wb.screenshot both need it. keymap.library and graphics.library were missing too.
• input.*, sandbox.* and wb.screenshot had no per-feature prerequisite entries. That table is the one a user reads after a NotCapable, and it didn't mention the three newest features. input.* now spells out both gates; sandbox.* covers the SandboxVM binary and the ExtMem requirement.
• CONTRIBUTING.md said "branch from main" — the protected release branch. That is exactly why input.*: keyboard and mouse injection, disabled by default #2 arrived aimed at main and needed rebasing. It now says develop, and explains why.
• Neither README nor USAGE mentioned wb.screenshot, and USAGE's namespace table was missing input.* and sandbox.*.
• Daemon source layouts in BUILD.md and mcpd/README.md were two modules stale, the binary size ~100 KiB out, and the install-script list missing the two input scripts.
• No quick start. The README described the system well but never showed the three commands that get someone to a working session.

Newly documented behaviours

Both cost real debugging time and neither was written down anywhere public:

• The AmigaOS kernel debug buffer does not wrap. Once full it stops accepting entries, so on a machine with a verbose driver sys.debug_ring can be blind to everything logged after boot. Compare raw_size across two calls to tell "full" from "quiet"; serial.* is unaffected.
• While a board is powered off, only power.on / power.off are safe to send to the MCU. Other shell commands can leave a cold MCU unresponsive until mains power is cut.

Framing

Shifted from how the project got here to what it does: supported targets became a status matrix, "Status" became "Requirements", and BUILD's source-of-truth note now points at --list-tools and proto.capabilities rather than describing the docs as a record of intent.

🤖 Generated with Claude Code

https://claude.ai/code/session_01VF4wwBXaKNK2Y2N5sYtt71