release v0.12.0

- **`agent-shape.toml`** at the repo root with `[commands].top_level`
  enumerating 19 subcommands. Cross-validated against the binary via
  `jig check --binary` so the shape file and the actual CLI surface
  cannot drift apart silently.
- **`scripts/agent-shape-fixture.sh`**, an idempotent fixture script
  that seeds 3 registries for agent-shape tuning runs. Re-running it
  is safe; existing state is left untouched.
- **5 tuning tasks** under the agent-shape workflow plus a first
  baseline (n=5).
- **Treatment v0** for first-contact discoverability:
  - `kit --help` now opens with a workflow preamble naming
    `kit status`, `kit pin`, `kit unpin`, and `kit verify-registry`
    so the first thing an agent reads points at the right entry
    points.
  - `kit skill` gains a first-contact section and worked examples.
  - `kit status` prints a soft mtime nudge when `kit.toml` is newer
    than the lockfile, pointing at `kit verify` to refresh derived
    state. Non-fatal; safe across coarse-mtime filesystems.
- **`hero.svg`** and **`avatar.svg`** in the nomograph paper-palette
  OV-1 style.
- **`CODEOWNERS`** at the repo root.

- README aligned with current state; aspirational claims dropped.