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/migration.test.ts

@@ -37,7 +37,7 @@ describe("migrateAgentNames", () => {
     const agents = {
       oracle: { model: "openai/gpt-5.2" },
       librarian: { model: "google/gemini-3-flash" },
-      explore: { model: "opencode/grok-code" },
+      explore: { model: "opencode/gpt-5-nano" },
     }
 
     // #when: Migrate agent names
@@ -47,7 +47,7 @@ describe("migrateAgentNames", () => {
     expect(changed).toBe(false)
     expect(migrated["oracle"]).toEqual({ model: "openai/gpt-5.2" })
     expect(migrated["librarian"]).toEqual({ model: "google/gemini-3-flash" })
-    expect(migrated["explore"]).toEqual({ model: "opencode/grok-code" })
+    expect(migrated["explore"]).toEqual({ model: "opencode/gpt-5-nano" })
   })
 
   test("handles case-insensitive migration", () => {
@@ -418,7 +418,7 @@ describe("migrateAgentConfigToCategory", () => {
   test("migrates model to category when mapping exists", () => {
     // #given: Config with a model that has a category mapping
     const config = {
-      model: "google/gemini-3-pro-preview",
+      model: "google/gemini-3-pro",
       temperature: 0.5,
       top_p: 0.9,
     }
@@ -467,7 +467,7 @@ describe("migrateAgentConfigToCategory", () => {
   test("handles all mapped models correctly", () => {
     // #given: Configs for each mapped model
     const configs = [
-      { model: "google/gemini-3-pro-preview" },
+      { model: "google/gemini-3-pro" },
       { model: "openai/gpt-5.2" },
       { model: "anthropic/claude-haiku-4-5" },
       { model: "anthropic/claude-opus-4-5" },
@@ -536,7 +536,7 @@ describe("shouldDeleteAgentConfig", () => {
     // #given: Config with fields matching category defaults
     const config = {
       category: "visual-engineering",
-      model: "google/gemini-3-pro-preview",
+      model: "google/gemini-3-pro",
     }
 
     // #when: Check if config should be deleted
@@ -664,7 +664,7 @@ describe("migrateConfigFile with backup", () => {
       agents: {
         "multimodal-looker": { model: "anthropic/claude-haiku-4-5" },
         oracle: { model: "openai/gpt-5.2" },
-        "my-custom-agent": { model: "google/gemini-3-pro-preview" },
+        "my-custom-agent": { model: "google/gemini-3-pro" },
       },
     }
 
@@ -680,7 +680,7 @@ describe("migrateConfigFile with backup", () => {
     const agents = rawConfig.agents as Record<string, Record<string, unknown>>
     expect(agents["multimodal-looker"].model).toBe("anthropic/claude-haiku-4-5")
     expect(agents.oracle.model).toBe("openai/gpt-5.2")
-    expect(agents["my-custom-agent"].model).toBe("google/gemini-3-pro-preview")
+    expect(agents["my-custom-agent"].model).toBe("google/gemini-3-pro")
   })
 
   test("preserves category setting when explicitly set", () => {