Task-shaped skills will draw their reference material (per-platform SDK
guides, per-signal concepts) from a single maintained library rather
than duplicating it. Each shipped skill must still be self-contained, so
the build copies a skill's declared references into it.
Add a CONTENT_ROOT env var (default: repo root) so the same build steps
can assemble an alternate skill tree, e.g. CONTENT_ROOT=skills-next.
hydrate-references.py walks a skills directory: for every skill with a
references.yml it brace-expands and globs the `needs:` patterns against
the library, copies the matches into the skill's references/ preserving
subpaths, and strips the manifest so it never ships. It runs via `uv run
--script` with inline PyYAML and braceexpand dependencies. build-common.sh
invokes it once per build, and only when some skill declares references,
so existing skills are unaffected and the common case spawns no
interpreter.
Factor the steps shared across all four agent builders into
build-common.sh (content-root resolution, skill copy+hydrate, commands,
SKILL_TREE), sourced by each plugin-src/<agent>/build.sh.
Evan Purkhiser