fix(models): update model names to match OpenCode Zen catalog (#1048)

* fix(models): update model names to match OpenCode Zen catalog

OpenCode Zen recently updated their official model catalog, deprecating
several preview and free model variants:

DEPRECATED → NEW (Official Zen Names):
- gemini-3-pro-preview → gemini-3-pro
- gemini-3-flash-preview → gemini-3-flash
- grok-code → gpt-5-nano (FREE tier maintained)
- glm-4.7-free → big-pickle (FREE tier maintained)
- glm-4.6v → glm-4.6

Changes:
- Updated 6 source files (model-requirements, delegate-task, think-mode, etc.)
- Updated 9 documentation files (installation, configurations, features, etc.)
- Updated 14 test files with new model references
- Regenerated snapshots to reflect catalog changes
- Removed duplicate think-mode entries for preview variants

Impact:
- FREE tier access preserved via gpt-5-nano and big-pickle
- All 55 model-related tests passing
- Zero breaking changes - pure string replacement
- Aligns codebase with official OpenCode Zen model catalog

Verified:
- Zero deprecated model names in codebase
- All model-related tests pass (55/55)
- Snapshots regenerated and validated

Affects: 30 files (6 source, 9 docs, 14 tests, 1 snapshot)

* fix(multimodal-looker): update fallback chain with glm-4.6v and gpt-5-nano

- Change glm-4.6 to glm-4.6v for zai-coding-plan provider
- Add opencode/gpt-5-nano as 4th fallback (FREE tier)
- Push gpt-5.2 to 5th position

Fallback chain now:
1. gemini-3-flash (google, github-copilot, opencode)
2. claude-haiku-4-5 (anthropic, github-copilot, opencode)
3. glm-4.6v (zai-coding-plan)
4. gpt-5-nano (opencode) - FREE
5. gpt-5.2 (openai, github-copilot, opencode)

* chore: update bun.lock

---------

Co-authored-by: justsisyphus <justsisyphus@users.noreply.github.com>

src/shared/model-availability.test.ts

@@ -80,7 +80,7 @@ describe("fetchAvailableModels", () => {
       openai: { id: "openai", models: { "gpt-5.2-codex": { id: "gpt-5.2-codex" } } },
       anthropic: { id: "anthropic", models: { "claude-sonnet-4-5": { id: "claude-sonnet-4-5" } } },
       google: { id: "google", models: { "gemini-3-flash": { id: "gemini-3-flash" } } },
-      opencode: { id: "opencode", models: { "grok-code": { id: "grok-code" } } },
+      opencode: { id: "opencode", models: { "gpt-5-nano": { id: "gpt-5-nano" } } },
     })
 
     const result = await fetchAvailableModels()
@@ -89,7 +89,7 @@ describe("fetchAvailableModels", () => {
     expect(result.has("openai/gpt-5.2-codex")).toBe(true)
     expect(result.has("anthropic/claude-sonnet-4-5")).toBe(true)
     expect(result.has("google/gemini-3-flash")).toBe(true)
-    expect(result.has("opencode/grok-code")).toBe(true)
+    expect(result.has("opencode/gpt-5-nano")).toBe(true)
   })
 })