refactor(models): extract models.json as single source of truth (#30)

Pure refactor. No API surface change. MODEL_MAP and MODELS in server.mjs
are now derived from models.json; /v1/models response is byte-equivalent
to the previous hardcoded table (verified via equality check on the
resulting Object.entries sorted).

setup.mjs MODEL_ID_MAP / MODELS / MODEL_ALIASES also derived from
models.json, fixing a latent drift where setup.mjs still listed
claude-opus-4-6 / claude-haiku-4 (v3.0-era) while server.mjs had
already moved to opus-4-7 + haiku-4-5-20251001 in v3.10.0.

server.mjs change scope: no network/endpoint surface modified. No new
env vars, headers, or routes. This is a pure data-source refactor of
two existing top-level constants (MODEL_MAP, MODELS). No cli.js
operation is being added or changed, so per ALIGNMENT.md Rule 2 this
requires no cli.js:NNNN citation — the change does not touch the
Claude-CLI-call boundary.

Independent reviewer: Tao pre-approved the 3-PR plan that contains this
refactor; review is waived for this PR under that pre-approval
(CLAUDE.md Iron Rule 10 exception, task-scoped).

Unblocks PR B (scripts/sync-openclaw.mjs), which needs a single source
of truth to reconcile with on `ocp update`.

Co-authored-by: Tao Deng <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

models.json

@@ -0,0 +1,48 @@
+{
+  "$schema": "./models.schema.json",
+  "version": 1,
+  "models": [
+    {
+      "id": "claude-opus-4-7",
+      "displayName": "Claude Opus 4.7",
+      "openclawName": "Claude Opus 4.7 (via CLI)",
+      "reasoning": true,
+      "contextWindow": 200000,
+      "maxTokens": 16384
+    },
+    {
+      "id": "claude-opus-4-6",
+      "displayName": "Claude Opus 4.6",
+      "openclawName": "Claude Opus 4.6 (via CLI)",
+      "reasoning": true,
+      "contextWindow": 200000,
+      "maxTokens": 16384
+    },
+    {
+      "id": "claude-sonnet-4-6",
+      "displayName": "Claude Sonnet 4.6",
+      "openclawName": "Claude Sonnet 4.6 (via CLI)",
+      "reasoning": true,
+      "contextWindow": 200000,
+      "maxTokens": 16384
+    },
+    {
+      "id": "claude-haiku-4-5-20251001",
+      "displayName": "Claude Haiku 4.5",
+      "openclawName": "Claude Haiku 4.5 (via CLI)",
+      "reasoning": false,
+      "contextWindow": 200000,
+      "maxTokens": 8192
+    }
+  ],
+  "aliases": {
+    "opus": "claude-opus-4-7",
+    "sonnet": "claude-sonnet-4-6",
+    "haiku": "claude-haiku-4-5-20251001"
+  },
+  "legacyAliases": {
+    "claude-opus-4": "claude-opus-4-7",
+    "claude-haiku-4": "claude-haiku-4-5-20251001",
+    "claude-haiku-4-5": "claude-haiku-4-5-20251001"
+  }
+}