re #230 feat(scaffold): ship an AGENT.md in the module skeleton

[tonydspaniard]

Closes #230.

Problem

bin/altair module:new generates a module with only a human-oriented README.md. The host skeleton ships agent guidance (.ai/skills/altair/SKILL.md + .claude/skills/altair/), but that skill is bin/altair-driven and assumes a running host app — a standalone module has neither. So an agent dropped into a scaffolded module gets zero Univeros-specific orientation.

Observed in a real session building a module: it picked a forbidden univeros/* name + Univeros\* namespace, guessed at the spec:scaffold YAML vocabulary (not vendored in the module), and hand-built from the raw template instead of running module:new. A single agent guide would have prevented all three.

Change

Add a placeholder-templated AGENT.md to the module skeleton. SkeletonGenerator rewrites its vendor/module / VendorModule\ tokens like every other file (the non-.php branch replaces VendorModule\ and vendor/module), so the emitted guide carries the module's real package name and namespace.

It covers, module-focused and agent-agnostic:

• The one rule — own vendor/namespace, never Altair\* or univeros/*.
• ModuleInterface + the opt-in capability contracts (Routes / Middleware / Entity dirs / Migration dirs) — implement only what you ship.
• The Action -> Input(DTO) -> Domain -> Responder lifecycle; follow the generated Sample* as the pattern.
• Coding conventions (declare(strict_types=1), immutability, native types, small files, tests-first).
• The isolated dev/test loop (composer install && vendor/bin/phpunit — no host needed).
• The spec:scaffold caveat: the YAML vocabulary lives in the framework, not in this package — confirm with bin/altair spec:show, or hand-write following the sample.
• Host wiring (config/modules.php + the one schema binding) and the publish step.
• Links to the canonical extending.md / module.md.

MakeModuleCommandTest now asserts the AGENT.md is generated and fully rewritten (package name + namespace substituted, no leftover vendor/module / VendorModule\).

Note (not a bug)

The reported "composer.json still says vendor/module / VendorModule\" is not a scaffolder bug — module:new rewrites composer.json and source correctly (verified). That mismatch came from hand-building off the raw template; this PR doesn't change that, but the new AGENT.md tells agents to scaffold with module:new and keep the generated name/namespace.

Test plan

• module:new emits a rewritten AGENT.md (# AGENT.md — acme/polaris, Acme\Polaris\Module, no placeholders); file count 12 -> 13.
• MakeModuleCommandTest — 2 tests / 16 assertions, green.
• tests/Bootstrap — 22 tests green.
• composer cs / composer stan (level 8) / composer rector — clean.
• CI: 8.3 + 8.4, Static Analysis, Determinism gate.