feat(agents): keep dependencies' AGENTS.consumer.md in AGENTS.md

An agent working on a crafter-build project reads its AGENTS.md, and
learns nothing there about the libraries the project builds against
unless someone copied that in by hand. This repository shows the cost:
the code style section of its AGENTS.md restates what Crafter.LintRules
enforces, and goes stale whenever the rules change.

A library now ships those notes itself, as AGENTS.consumer.md beside
its project.cpp; nothing in its project.cpp changes. When a consumer
has an AGENTS.md beside its own project.cpp, `crafter-build` and
`crafter-build test` keep a section in it, between two marker comments,
holding its dependencies' notes. The section is appended the first time
and rewritten in place after that. The file is written only when the
section changes, and an AGENTS.md is never created. lint, format, run
and clean leave it alone. The update runs after loading, which has just
fetched every dependency, and before compiling, so a build that fails
still has the notes.

cfg.dependencyNotes picks the dependencies. Transitive, the default,
follows `dependencies` all the way down from the project's own
configurations, its tests and its `#pragma crafter dependency` tooling;
Direct stops at the first loaded project on each path; None removes
the section. A dependency's own pragma tooling never counts: it is
about how that dependency is built, not how it is used, and being no
`dependencies` edge it is never reached. Nor are a dependency's tests:
nothing builds them for the consumer, and their configurations can
point at a local their project file has since moved out of.

The walk has to know which Configurations belong to another project,
and where that project lives, and cfg.path cannot say: only the
Configuration GitProject and LocalProject return is rebased, so a
dependency's internal configurations keep "./", which resolves to the
consumer. The loader records it instead, LoadedProjectOf beside the
project cache, and keeps what the root's pragmas resolved to past the
frame LoadProject pops, PragmaDependencies. Neither is exported.

The markers count only as whole lines outside fenced code blocks, so
documentation can quote them. Unbalanced markers and a document ending
inside a code block leave the file alone with a warning: guessing which
part of someone's file is generated would overwrite their text, and
missing the section would add another one on every build. A note that
would break the section when it is read back, through a marker line of
its own or a code block it never closes, is left out with a warning.
The file is replaced through a temporary renamed onto the symlink's
target, so a linked AGENTS.md stays a link and a write cut short leaves
the old file rather than part of the new one.

The code is a new partition, Crafter.Build:Agents, listed in build.sh,
CrafterBuildModules, project.cpp and the umbrella.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

build.sh

@@ -48,7 +48,7 @@ cp wasi-runtime/index.html.in share/crafter-build/wasi-runtime/
 
 # Partition order is the import order: every unit is listed before the
 # units that import it, and the umbrella last.
-PARTITIONS="Toolchain Shader Platform Interface Implementation External Clang Test Lint Script Progress Asset"
+PARTITIONS="Toolchain Shader Platform Interface Implementation External Agents Clang Test Lint Script Progress Asset"
 
 cp interfaces/Crafter.Build.cppm share/crafter-build/
 for p in $PARTITIONS; do