fix(docs): revert wrong schema URL canonicalization (file is oh-my-opencode.schema.json)

In #3859 I bulk-replaced `oh-my-opencode.schema.json` ->
`oh-my-openagent.schema.json` across docs/, on the false assumption
that the schema file had been renamed alongside the package.

It hadn't. Repo state on dev:

- assets/oh-my-opencode.schema.json (only file present)
- package.json export `./schema.json` -> `./dist/oh-my-opencode.schema.json`
- script/build-schema.ts emits the same legacy basename
- root AGENTS.md line 135 documents the same legacy URL

So every doc that pointed at `oh-my-openagent.schema.json` was
returning HTTP 404 for any user copying the example into their config.

Verified live:

  https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json -> 404
  https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json -> 200

Files reverted to canonical legacy URL:

- docs/examples/{coding,default,planning}-focused.jsonc
- docs/guide/{overview,installation,agent-model-matching}.md
- docs/reference/configuration.md (2 occurrences)

docs/examples/coding-focused.jsonc

@@ -1,5 +1,5 @@
 {
-  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json",
+  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
 
   // Optimized for intensive coding sessions.
   // Prioritizes deep implementation agents and fast feedback loops.

docs/examples/default.jsonc

@@ -1,5 +1,5 @@
 {
-  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json",
+  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
 
   // Balanced defaults for general development.
   // Tuned for reliability across diverse tasks without overspending.

docs/examples/planning-focused.jsonc

@@ -1,5 +1,5 @@
 {
-  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json",
+  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
 
   // Optimized for strategic planning, architecture, and complex project design.
   // Prioritizes deep thinking agents and thorough analysis before execution.

docs/guide/agent-model-matching.md

@@ -337,7 +337,7 @@ See the [Orchestration System Guide](./orchestration.md) for how agents dispatch
 
 ```jsonc
 {
-  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json",
+  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
 
   "agents": {
     // Sisyphus: Kimi K2.6 is the top alternative to Claude for orchestration

docs/guide/installation.md

@@ -38,7 +38,7 @@ Core CLI subcommands are: `install`, `run`, `doctor`, `mcp-oauth`, `refresh-mode
 Config schema URL:
 
 ```json
-"$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json"
+"$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json"
 ```
 
 Operational notes:

docs/guide/overview.md

@@ -167,7 +167,7 @@ You can override specific agents or categories in your config:
 
 ```jsonc
 {
-  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json",
+  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
 
   "agents": {
     // Main orchestrator: Claude Opus or Kimi K2.5 work best

docs/reference/configuration.md

@@ -62,7 +62,7 @@ Enable schema autocomplete:
 
 ```json
 {
-  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json"
+  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json"
 }
 ```
 
@@ -74,7 +74,7 @@ Here's a practical starting configuration:
 
 ```jsonc
 {
-  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-openagent.schema.json",
+  "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
 
   "agents": {
     // Main orchestrator: Claude Opus or Kimi K2.5 work best