feat(coding-agent): extended --thinking CLI flag options

- Added `off` and `auto` as valid inputs for the `--thinking` CLI flag.
- Centralized thinking level definitions in `CLI_THINKING_LEVELS` to keep flag options, shell completions, and validation in sync.
- Configured CLI parsing to reject `inherit` as an explicit input to prevent unintended configuration suppression.

packages/coding-agent/test/cli/completions.test.ts

@@ -211,7 +211,7 @@ describe("omp completions (integration / drift)", () => {
 		}
 		expect(stdout).toContain("{-r,--resume}");
 		// Real enum option sets flow through unchanged.
-		expect(stdout).toContain(":value:(minimal low medium high xhigh)");
+		expect(stdout).toContain(":value:(off minimal low medium high xhigh auto)");
 		expect(stdout).toContain(":value:(always-ask write yolo)");
 		// Real subcommands present; dynamic callbacks wired.
 		expect(stdout).toContain("_omp_cmd_commit");