fix(docs,test): restore the dropped Opus 4.8 line; assert the window CEILING

Two review findings from the independent Iron-Rule-10 reviewer, both confirmed
before applying:

1. docs/lan-mode.md: the sample `ocp update` output lost `ocp/claude-opus-4-8`
   entirely — the edit substituted the id instead of inserting the new one, so
   the block listed 6 bullets while line 219 of the same document claims
   "7 models available". Self-contradictory. Restored; the block is 7 again.

2. test-features.mjs: "every contextWindow is 200000" was too rigid and
   contradicted ADR 0009, which states the budget "scales automatically — no
   code change". Asserting every entry turned that documented no-code-change
   path into a must-edit-tests path, and would have failed on a future entry
   with a legitimately SMALLER window. Now asserts the MAX instead: raising the
   ceiling (the actual hazard, since the budget is global) still fails, while a
   smaller-window model stays legal.

Verified the reformulation is strictly better, not just different:
  - raise a window to 1000000  -> 2 failures (ceiling + derivePromptCharBudget SPOT)
  - add a legitimate 128k model -> 452 passed, 0 failed   (old test would have failed here)

Tests: 452 passed, 0 failed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017gbqUZ8HfBZpjjbzQ85oH8

docs/lan-mode.md

@@ -247,6 +247,7 @@ OCP Connect v1.3.0
     Provider: ocp
     Models:
       • ocp/claude-opus-5
+      • ocp/claude-opus-4-8
       • ocp/claude-opus-4-7
       • ocp/claude-opus-4-6
       • ocp/claude-sonnet-5