fix(ci): resolve all test failures + complete rename compat layer

Sisyphus-authored fixes across 15 files:

- plugin-identity: align CONFIG_BASENAME with actual config file name
- add-plugin-to-opencode-config: handle legacy→canonical name migration
- plugin-detection tests: update expectations for new identity constants
- doctor/system: fix legacy name warning test assertions
- install tests: align with new plugin name
- chat-params tests: fix mock isolation
- model-capabilities tests: fix snapshot expectations
- image-converter: fix platform-dependent test assertions (Linux CI)
- example configs: expanded with more detailed comments

Full suite: 4484 pass, 0 fail, typecheck clean.

src/shared/plugin-identity.test.ts

@@ -3,24 +3,24 @@ import { PLUGIN_NAME, CONFIG_BASENAME, LOG_FILENAME, CACHE_DIR_NAME } from "./pl
 
 describe("plugin-identity constants", () => {
   describe("PLUGIN_NAME", () => {
-    it("equals oh-my-opencode", () => {
+    it("equals oh-my-openagent", () => {
       // given
 
       // when
 
       // then
-      expect(PLUGIN_NAME).toBe("oh-my-opencode")
+      expect(PLUGIN_NAME).toBe("oh-my-openagent")
     })
   })
 
   describe("CONFIG_BASENAME", () => {
-    it("equals oh-my-opencode", () => {
+    it("equals oh-my-openagent", () => {
       // given
 
       // when
 
       // then
-      expect(CONFIG_BASENAME).toBe("oh-my-opencode")
+      expect(CONFIG_BASENAME).toBe("oh-my-openagent")
     })
   })