fix(bundler): read the authoritative default_integration field, not only its legacy aliases (#3880)

* fix(bundler): read the authoritative default_integration field

`active_integration()` resolves a project's integration with

    data.get("integration") or data.get("id") or data.get("active")

and never looks at `default_integration` — which is the key the CLI
actually writes. `integration_state.set_default_integration` persists
`data["default_integration"] = integration_key`, and the canonical
reader in that module orders it the other way round:

    key = state.get("default_integration") or state.get("integration")

So a project initialised by any current version of the CLI looks to the
bundler as though it has no active integration:

    {"default_integration": "copilot"}  -> None      (expected "copilot")
    {"integration": "copilot"}          -> "copilot" (legacy alias)

That silently changes bundler behaviour that keys off the active
integration, including the FR-019 clash guard, which treats an
undeterminable integration differently from a known one.

Read `default_integration` first and keep the three legacy aliases as
fallbacks for projects initialised by older versions.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* docs(bundler): correct the justification for reading default_integration

Review catch: the comment cited a nonexistent
`integration_state.set_default_integration` and overstated the impact.
The real writer is `write_integration_json`, which persists BOTH
`integration` and `default_integration` (integration_state.py:248-250), so
a marker produced by the current CLI already resolved through the
`integration` alias. Measured:

  {"integration": "copilot", "default_integration": "copilot"} -> 'copilot'
  {"default_integration": "copilot"}                           -> 'copilot' (after fix)

Reword both the source comment and the test docstring: this is about which
field is authoritative when they disagree, plus resolving a marker that
carries only `default_integration` — not about every current project being
undetectable. The precedence itself still has its precedent, the canonical
reader at integration_state.py:199.

Behaviour unchanged; comments and docstrings only.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/specify_cli/bundler/lib/project.py

@@ -82,7 +82,21 @@ def active_integration(project_root: Path) -> str | None:
     except BundlerError:
         return None
     if isinstance(data, dict):
-        value = data.get("integration") or data.get("id") or data.get("active")
+        # ``default_integration`` first, matching the canonical reader in
+        # ``integration_state`` (line 199):
+        # ``state.get("default_integration") or state.get("integration")``.
+        # ``write_integration_json`` writes both keys, so a marker produced by
+        # the current CLI already resolved through the ``integration`` alias --
+        # this is about which field is authoritative when they disagree, and
+        # about resolving a marker that carries only ``default_integration``
+        # (hand-edited, or written by anything that follows the canonical
+        # reader's shape). ``integration``/``id``/``active`` stay as fallbacks.
+        value = (
+            data.get("default_integration")
+            or data.get("integration")
+            or data.get("id")
+            or data.get("active")
+        )
         if isinstance(value, str) and value:
             return value
     return None

tests/integration/test_bundler_security_paths.py

@@ -126,6 +126,50 @@ def test_active_integration_refuses_symlinked_specify_escape(tmp_path: Path):
     assert active_integration(project) is None
 
 
+def _write_marker(tmp_path: Path, payload: str) -> Path:
+    project = tmp_path / "proj"
+    (project / ".specify").mkdir(parents=True)
+    (project / ".specify" / "integration.json").write_text(
+        payload, encoding="utf-8"
+    )
+    return project
+
+
+def test_active_integration_reads_default_integration(tmp_path: Path):
+    """A marker carrying only ``default_integration`` must resolve.
+
+    ``write_integration_json`` writes both ``integration`` and
+    ``default_integration``, so a marker produced by the current CLI already
+    resolved through the alias. This covers the authoritative field on its own —
+    hand-edited, or written by anything that follows the shape of the canonical
+    reader (``integration_state`` line 199:
+    ``state.get("default_integration") or state.get("integration")``).
+    """
+    from specify_cli.bundler.lib.project import active_integration
+
+    project = _write_marker(tmp_path, '{"default_integration": "copilot"}')
+    assert active_integration(project) == "copilot"
+
+
+def test_active_integration_prefers_default_over_legacy_alias(tmp_path: Path):
+    """When both are present the authoritative field wins, matching
+    ``integration_state``'s own ordering."""
+    from specify_cli.bundler.lib.project import active_integration
+
+    project = _write_marker(
+        tmp_path, '{"integration": "stale", "default_integration": "copilot"}'
+    )
+    assert active_integration(project) == "copilot"
+
+
+def test_active_integration_still_reads_legacy_alias(tmp_path: Path):
+    """Projects initialised by older versions carry only ``integration``."""
+    from specify_cli.bundler.lib.project import active_integration
+
+    project = _write_marker(tmp_path, '{"integration": "copilot"}')
+    assert active_integration(project) == "copilot"
+
+
 def test_read_catalog_config_refuses_symlinked_specify_escape(tmp_path: Path):
     from specify_cli.bundler.commands_impl import catalog_config as cc