merge: absorb main into next — 23-commit divergence (08-05..13 base=main window)

17 content commits + 3 merge bubbles were genuinely missing from next (~8,000 lines:
goal controller #1152, framework enforcement #1174/#1195, pr-edit wrapper #1173/#1200,
pipefail series #1100/#1105/#1106/#1107, git-tools fixes #1073/#1085/#1086/#1089,
#991, #1007, enrollment tolerance #1094). 3 commits were already in next by content
(#1060 identical, #1066/#1062 evolved twins — conflicts resolved to next's side).

Per-commit classification and evidence: mosaic-brain fleet/lanes/stack-remediation/main-next-divergence.md.
Conflict resolutions (6 files) itemized in the PR body.

packages/mosaic/src/commands/launch.spec.ts

@@ -5,6 +5,7 @@ import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import {
   buildPiSkillArgs,
+  discoverPiExtensionArgs,
   enumerateSkillDirs,
   piForceSkillNames,
   registerRuntimeLaunchers,
@@ -178,6 +179,52 @@ describe('buildPiSkillArgs', () => {
   });
 });
 
+describe('discoverPiExtensionArgs', () => {
+  it('loads the core and goal extensions in deterministic order from Mosaic home', () => {
+    const root = mkdtempSync(join(tmpdir(), 'mosaic-pi-extensions-'));
+    const runtimeDir = join(root, 'runtime', 'pi');
+    mkdirSync(runtimeDir, { recursive: true });
+    writeFileSync(join(runtimeDir, 'goal-extension.ts'), '// goal\n');
+    writeFileSync(join(runtimeDir, 'mosaic-extension.ts'), '// core\n');
+
+    try {
+      expect(discoverPiExtensionArgs(root)).toEqual([
+        '--extension',
+        join(runtimeDir, 'mosaic-extension.ts'),
+        '--extension',
+        join(runtimeDir, 'goal-extension.ts'),
+      ]);
+    } finally {
+      rmSync(root, { recursive: true, force: true });
+    }
+  });
+
+  it('remains backward-compatible when the optional goal extension is absent', () => {
+    const root = mkdtempSync(join(tmpdir(), 'mosaic-pi-extensions-'));
+    const runtimeDir = join(root, 'runtime', 'pi');
+    mkdirSync(runtimeDir, { recursive: true });
+    writeFileSync(join(runtimeDir, 'mosaic-extension.ts'), '// core\n');
+
+    try {
+      expect(discoverPiExtensionArgs(root)).toEqual([
+        '--extension',
+        join(runtimeDir, 'mosaic-extension.ts'),
+      ]);
+    } finally {
+      rmSync(root, { recursive: true, force: true });
+    }
+  });
+
+  it('emits no extension arguments when Mosaic runtime assets are absent', () => {
+    const root = mkdtempSync(join(tmpdir(), 'mosaic-pi-extensions-'));
+    try {
+      expect(discoverPiExtensionArgs(root)).toEqual([]);
+    } finally {
+      rmSync(root, { recursive: true, force: true });
+    }
+  });
+});
+
 describe('enumerateSkillDirs (real FS)', () => {
   let root: string;