fix(#4705): emit Antigravity-native tool names as a YAML sequence (#4822)

* test(#4705): add failing-first coverage for native Antigravity tool sequences

* fix(#4705): emit Antigravity-native tool names as a YAML sequence

convertClaudeAgentToAntigravityAgent and the installer's twin emitted
Gemini CLI tool names as a comma-separated scalar. Antigravity's
documented subagent contract (antigravity.google/docs/subagents) wants a
YAML sequence of native names — view_file, grep_search, run_command,
replace_file_content are the documented examples, and wrong or malformed
grants can hang the subagent per Antigravity's own warning.

Map values move to the native vocabulary where documented (Read ->
view_file, Edit -> replace_file_content, Bash -> run_command, Grep ->
grep_search); undocumented entries keep their best-known grant rather
than being dropped (dropping would silently remove a restriction). The
emitter writes one '- name' item per line; an agent whose every tool was
filtered emits an explicit tools: [] instead of an empty scalar.
Pre-existing pins updated to the native vocabulary.

* test(#4705): update the #4727 map-value pin to the Antigravity-native vocabulary

The #4727-era pin held the map VALUES at the Gemini CLI dialect on the
belief that Antigravity speaks it; the confirmed bug #4705 (with
Antigravity's own documented subagent contract) supersedes that for the
four documented names. Key/shape pinning is preserved; only the values
move.

* docs(#4705): backfill changeset PR number

---------

Co-authored-by: sim <sim@local>

tests/runtime-converters.test.cjs

@@ -478,12 +478,12 @@ tools: Read, Write, Bash, Skill, WebFetch, SlashCommand
 <role>Plan the phase.</role>`;
 
     const result = convertClaudeAgentToAntigravityAgent(input);
-    const toolsLine = result.split('\n').find(l => l.startsWith('tools:')) || '';
+    const toolsItems = result.split('\n').filter(l => l.startsWith('- ')).map(l => l.slice(2));
 
-    assert.ok(toolsLine.includes('read_file'), 'maps Read -> read_file');
-    assert.ok(toolsLine.includes('web_fetch'), 'maps WebFetch -> web_fetch');
-    assert.ok(!/\bskill\b/.test(toolsLine), 'no invalid skill tool in Antigravity frontmatter');
-    assert.ok(!/\bslashcommand\b/.test(toolsLine), 'no invalid slashcommand tool in Antigravity frontmatter');
+    assert.ok(toolsItems.includes('view_file'), 'maps Read -> view_file (#4705 native name)');
+    assert.ok(toolsItems.includes('web_fetch'), 'maps WebFetch -> web_fetch');
+    assert.ok(!toolsItems.some(t => /\bskill\b/.test(t)), 'no invalid skill tool in Antigravity frontmatter');
+    assert.ok(!toolsItems.some(t => /\bslashcommand\b/.test(t)), 'no invalid slashcommand tool in Antigravity frontmatter');
   });
 });
 
@@ -2667,3 +2667,40 @@ describe('#3706: the layout seam actually threads the variant', () => {
     }
   });
 });
+
+// ── #4705 — Antigravity agent tools: native names, YAML sequence ─────────────
+// The converter emitted Gemini CLI tool names as a comma-separated scalar;
+// Antigravity's documented subagent contract (antigravity.google/docs/subagents)
+// wants a YAML sequence of native tool names (view_file, grep_search,
+// run_command, replace_file_content are the documented examples). A scalar or a
+// wrong-vocabulary grant can hang the subagent per Antigravity's own warning.
+describe('#4705 — Antigravity agent tools are native names in a YAML sequence', () => {
+  const input = `---
+name: example-reviewer
+description: Inspect source files
+tools: Read, Grep, Bash
+---
+
+Inspect source files.`;
+
+  test('emits the documented native tools as a YAML sequence (#4705)', () => {
+    const result = convertClaudeAgentToAntigravityAgent(input);
+    assert.match(result, /tools:\n- view_file\n- grep_search\n- run_command\n/,
+      'tools must be a YAML sequence of Antigravity-native names (view_file, grep_search, run_command)');
+    assert.doesNotMatch(result, /tools:.*,/m, 'no comma-separated scalar may survive');
+  });
+
+  test('Edit maps to the documented replace_file_content (#4705)', () => {
+    const result = convertClaudeAgentToAntigravityAgent(
+      `---\nname: e\ndescription: d\ntools: Edit\n---\n\nbody`);
+    assert.match(result, /- replace_file_content/, 'Edit -> replace_file_content (documented native name)');
+    assert.ok(!/- replace\b/.test(result), 'the Gemini CLI name replace must not survive');
+  });
+
+  test('unmapped tools keep their lowercase grant (no silent restriction drop) (#4705)', () => {
+    const result = convertClaudeAgentToAntigravityAgent(
+      `---\nname: e\ndescription: d\ntools: Glob, WebFetch\n---\n\nbody`);
+    assert.match(result, /- glob/, 'undocumented tools keep their mapped/lowercase grant');
+    assert.match(result, /- web_fetch/, 'WebFetch stays granted');
+  });
+});