docs+cli: require <provider>/ prefix on every model id

Every CLI model id now resolves to a route in providers.routes via
its leading <provider>/ segment (skvm strips the first slash-segment
before the backend SDK sees the id). Unprefixed ids used to silently
fall through to OpenRouter; they now error out with a route-match
failure.

- Docs and README: switch command examples to <provider>/<model-id>
  placeholders and add a short intro paragraph explaining the shape;
  keep concrete ids only where the reader needs runnable recipes
  (providers.md, jiuwenclaw.md) or factual inventory (README bundled
  profiles list).
- CLI help/error text: same placeholder convention in --help output,
  missing-flag error messages, and JSDoc examples.
- Bundled profile dirs (skvm-data submodule): rekey with openrouter/
  prefix — all existing profiles were produced via OR, so their CLI
  ids are openrouter/<vendor>/<model>.
- Tests: update fixtures that used bare <vendor>/<model> ids. Keep
  the rejection test for unprefixed ids in registry.test.ts.

fix opencode resolution for npm-installed skvm, split bench vs headle…

…ss resolvers

The compiled skvm binary couldn't find its bundled opencode: inside a Bun
single-file executable, process.execPath is a virtual /\$bunfs path, so
deriving the install root from it pointed at a non-existent location and
silently fell through to the user's global opencode. Fix by having bin/skvm.js
hand the real on-disk install root to the child via SKVM_INSTALL_ROOT env var.

Also split resolveOpenCodeCmd into two purpose-specific resolvers so the
benchmark target (OpenCodeAdapter — measure user's real install) and the
internal tuner (runHeadlessAgent — reproducible, pinned) can diverge:

  - resolveAdapterOpenCodeCmd: adapters.opencode → global → bundled
  - resolveHeadlessOpenCodeCmd: headlessAgent.opencodePath → bundled → global

Added headlessAgent.opencodePath config field for explicit headless override.
Memoized the headless resolver since jit-optimize / jit-boost call it in
hot loops.

bump version to 0.1.4

bump version to 0.1.3

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>