feat(environment): introduce disable_omo_env configuration option

- Added a new configuration option `disable_omo_env` to control the injection of the `<omo-env>` block in agent prompts.
- Updated relevant functions and tests to support this feature, ensuring that the environment context can be toggled on or off as needed.
- Enhanced documentation to reflect the new option and its implications for API cost and cache hit rates.

src/config/schema.test.ts

@@ -741,6 +741,59 @@ describe("ExperimentalConfigSchema feature flags", () => {
     }
   })
 
+  test("accepts disable_omo_env as true", () => {
+    //#given
+    const config = { disable_omo_env: true }
+
+    //#when
+    const result = ExperimentalConfigSchema.safeParse(config)
+
+    //#then
+    expect(result.success).toBe(true)
+    if (result.success) {
+      expect(result.data.disable_omo_env).toBe(true)
+    }
+  })
+
+  test("accepts disable_omo_env as false", () => {
+    //#given
+    const config = { disable_omo_env: false }
+
+    //#when
+    const result = ExperimentalConfigSchema.safeParse(config)
+
+    //#then
+    expect(result.success).toBe(true)
+    if (result.success) {
+      expect(result.data.disable_omo_env).toBe(false)
+    }
+  })
+
+  test("disable_omo_env is optional", () => {
+    //#given
+    const config = { safe_hook_creation: true }
+
+    //#when
+    const result = ExperimentalConfigSchema.safeParse(config)
+
+    //#then
+    expect(result.success).toBe(true)
+    if (result.success) {
+      expect(result.data.disable_omo_env).toBeUndefined()
+    }
+  })
+
+  test("rejects non-boolean disable_omo_env", () => {
+    //#given
+    const config = { disable_omo_env: "true" }
+
+    //#when
+    const result = ExperimentalConfigSchema.safeParse(config)
+
+    //#then
+    expect(result.success).toBe(false)
+  })
+
   test("rejects non-boolean hashline_edit", () => {
     //#given
     const config = { hashline_edit: "true" }