fix(#2544): exit 1 on missing key in config-get (#2588)

The configGet query handler previously threw GSDError with
ErrorClassification.Validation, which maps to exit code 10. Callers
using `if ! gsd-sdk query config-get key; then fallback; fi` could
not detect missing keys through the exit code alone, because exit 10
is still truthy-failure but the intent (and documented UNIX
convention — cf. `git config --get`) is exit 1 for absent key.

Change the classification for the two 'Key not found' throw sites to
ErrorClassification.Execution so the CLI exits 1 on missing key.
Usage/schema errors (no key argument, malformed JSON, missing
config.json) remain Validation.

Closes #2544

sdk/src/query/config-query.test.ts

@@ -6,7 +6,7 @@ import { describe, it, expect, beforeEach, afterEach } from 'vitest';
 import { mkdtemp, writeFile, mkdir, rm } from 'node:fs/promises';
 import { join } from 'node:path';
 import { tmpdir } from 'node:os';
-import { GSDError } from '../errors.js';
+import { GSDError, ErrorClassification, exitCodeFor } from '../errors.js';
 
 // ─── Test setup ─────────────────────────────────────────────────────────────
 
@@ -58,6 +58,41 @@ describe('configGet', () => {
     await expect(configGet(['nonexistent.key'], tmpDir)).rejects.toThrow(GSDError);
   });
 
+  it('throws GSDError that maps to exit code 1 for missing key (bug #2544)', async () => {
+    const { configGet } = await import('./config-query.js');
+    await writeFile(
+      join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({ model_profile: 'quality' }),
+    );
+    try {
+      await configGet(['nonexistent.key'], tmpDir);
+      throw new Error('expected configGet to throw for missing key');
+    } catch (err) {
+      expect(err).toBeInstanceOf(GSDError);
+      const gsdErr = err as GSDError;
+      // UNIX convention: missing config key should exit 1 (like `git config --get`).
+      // Validation (exit 10) is the previous buggy classification — see issue #2544.
+      expect(gsdErr.classification).toBe(ErrorClassification.Execution);
+      expect(exitCodeFor(gsdErr.classification)).toBe(1);
+    }
+  });
+
+  it('throws GSDError that maps to exit code 1 when traversing into non-object (bug #2544)', async () => {
+    const { configGet } = await import('./config-query.js');
+    await writeFile(
+      join(tmpDir, '.planning', 'config.json'),
+      JSON.stringify({ model_profile: 'quality' }),
+    );
+    try {
+      await configGet(['model_profile.subkey'], tmpDir);
+      throw new Error('expected configGet to throw');
+    } catch (err) {
+      expect(err).toBeInstanceOf(GSDError);
+      const gsdErr = err as GSDError;
+      expect(exitCodeFor(gsdErr.classification)).toBe(1);
+    }
+  });
+
   it('reads raw config without merging defaults', async () => {
     const { configGet } = await import('./config-query.js');
     // Write config with only model_profile -- no workflow section

sdk/src/query/config-query.ts

@@ -104,12 +104,14 @@ export const configGet: QueryHandler = async (args, projectDir, _workstream) =>
   let current: unknown = config;
   for (const key of keys) {
     if (current === undefined || current === null || typeof current !== 'object') {
-      throw new GSDError(`Key not found: ${keyPath}`, ErrorClassification.Validation);
+      // UNIX convention (cf. `git config --get`): missing key exits 1, not 10.
+      // See issue #2544 — callers use `if ! gsd-sdk query config-get k; then` patterns.
+      throw new GSDError(`Key not found: ${keyPath}`, ErrorClassification.Execution);
     }
     current = (current as Record<string, unknown>)[key];
   }
   if (current === undefined) {
-    throw new GSDError(`Key not found: ${keyPath}`, ErrorClassification.Validation);
+    throw new GSDError(`Key not found: ${keyPath}`, ErrorClassification.Execution);
   }
 
   return { data: current };