skeleton: plugin layout + docs, skill/agent migration deferred to iter 1

Establishes the repository structure for the skills plugin:
- README + INSTALL describing the two-layer split (plugin
  mechanics vs per-project profile)
- docs/design, profile-schema, pipeline, agent-template covering
  the universal discipline constants and the profile slot model
- templates/project-profile.yml as a copy-and-fill starting point
- templates/CLAUDE.md.fragment with the baseline orchestrator
  rules a project can import
- install.sh / uninstall.sh wiring skills/ + agents/ into
  ~/.claude/ via idempotent symlinks
- skills/ and agents/ directories empty except for migration
  READMEs; the actual SKILL bodies and agent files migrate
  from ~/dev/ailang/skills/ in the next iteration.

No skill or agent runs yet — this commit only stands up the
structure and documents the substitution model.

INSTALL.md

@@ -0,0 +1,65 @@
+# Install
+
+## Prerequisites
+
+- Claude Code with `~/.claude/` writable
+- bash or any POSIX shell to run `install.sh`
+
+## One-time global install
+
+```sh
+git clone <repo-url> ~/dev/skills
+cd ~/dev/skills
+./install.sh
+```
+
+`install.sh` creates symlinks from `~/.claude/skills/` and
+`~/.claude/agents/` into this repo. Claude Code discovers them
+at session start under user-level skill and agent registries,
+so they become available in every project without further setup.
+
+To uninstall:
+
+```sh
+~/dev/skills/uninstall.sh
+```
+
+## Per-project activation
+
+A project opts in by dropping a profile file:
+
+```sh
+cp ~/dev/skills/templates/project-profile.yml \
+   <project-root>/.claude/dev-cycle-profile.yml
+$EDITOR <project-root>/.claude/dev-cycle-profile.yml
+```
+
+Edit the profile to match the project's paths, commands, and
+vocabulary. The skill bodies read the profile at the start of
+each invocation; there is no template-render step.
+
+A project that has not dropped a profile file gets sensible
+fallbacks (see `docs/profile-schema.md` for the defaults), but
+the discipline shines when the profile is explicit.
+
+## Per-project CLAUDE.md fragment
+
+The plugin handles mechanics. Project-specific *sittenkodex* —
+feature acceptance criteria, anti-patterns the project has
+earned the hard way, domain-specific contracts — belongs in the
+project's own `CLAUDE.md`. A starter fragment with the universal
+discipline sentences (only-orchestrator-commits, main sacrosanct,
+no nostalgia for removed features, etc.) lives in
+`templates/CLAUDE.md.fragment` for projects that want to import
+those baseline rules without rewriting them.
+
+## Update
+
+```sh
+cd ~/dev/skills && git pull
+```
+
+Symlinks pick up the changes automatically. If new skills or
+agents have been added, re-run `install.sh` to add the new
+symlinks (it is idempotent and will not overwrite existing
+ones).