fix: register extensions for the active integration only

extension add registered commands for every detected agent, and
integration upgrade back-filled enabled extensions for non-active
integrations. Maintainer direction on #2948: treat the project as
single-active. Only the active integration gets extension artifacts;
use/switch rescaffold the target when the user selects it.

- extension add now routes through the all-agents pass restricted to
  the active integration (only_agent), keeping detection and
  missing-skills-dir recovery safeguards. Projects without recorded
  init-options fall back to detection-based registration.
- integration upgrade re-registers extensions only when upgrading the
  active integration, reversing the #2886 back-fill for non-active
  targets at maintainer request.

Fixes #2948

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/specify_cli/integrations/_helpers.py

@@ -376,19 +376,14 @@ def _register_extensions_for_agent(
     """Register all enabled extensions' commands/skills for ``agent_key``.
 
     ``use`` / ``switch`` re-register enabled extensions for the agent they
-    activate; ``upgrade`` backfills them for the refreshed agent. Plain
-    ``install`` deliberately does not call this helper so adding a secondary
-    integration has no extension side effects until it is selected or upgraded.
-    See issue #2886.
+    activate (rescaffold); ``upgrade`` does so only for the *active*
+    integration. Plain ``install`` and upgrade of a non-active integration
+    deliberately skip this helper so a secondary integration has no extension
+    side effects until it is selected. See issues #2886 and #2948.
 
-    Known limitation: extension *skill* rendering is scoped to the active
-    agent (init-options track a single ``ai`` / ``ai_skills`` pair). A
-    skills-mode agent registered while it is *not* the active agent (e.g.
-    Copilot ``--skills`` registered while non-active) therefore
-    receives command files rather than skills here — matching ``extension
-    add``'s multi-agent behavior. ``use`` / ``switch`` avoid this because they
-    make the target the active agent first. Per-agent skills parity is tracked in
-    #2948.
+    Callers always pass the active agent (use/switch activate the target
+    before registering), so extension *skill* rendering — which is scoped to
+    the active ``ai`` / ``ai_skills`` init-options — matches ``agent_key``.
 
     Best-effort: never aborts the surrounding integration operation. Callers
     invoke it *after* the use/upgrade/switch transaction has committed so a

src/specify_cli/integrations/_migrate_commands.py

@@ -491,17 +491,19 @@ def integration_upgrade(
         if stale_removed:
             console.print(f"  Removed {len(stale_removed)} stale file(s) from previous install")
 
-    # Re-register enabled extensions for the upgraded agent so its extension
-    # commands are (re)created — including agents installed before this
-    # back-fill existed. Mirrors switch for command registration; see #2886.
-    # Done after the upgrade has fully settled (Phase 2 included) and outside
-    # the try/except above so this best-effort step cannot affect upgrade
-    # success.
-    _register_extensions_for_agent(
-        project_root,
-        key,
-        continuing="The integration was upgraded, but installed extensions may need re-registration.",
-    )
+    # Re-register enabled extensions only when upgrading the *active*
+    # integration, so its extension commands are (re)created after the
+    # upgrade settled (Phase 2 included). Done outside the try/except above
+    # so this best-effort step cannot affect upgrade success. Non-active
+    # integrations are rescaffolded by `use` / `switch` instead — the #2886
+    # back-fill for non-active agents was removed at maintainer request
+    # (#2948).
+    if key == installed_key:
+        _register_extensions_for_agent(
+            project_root,
+            key,
+            continuing="The integration was upgraded, but installed extensions may need re-registration.",
+        )
 
     name = (integration.config or {}).get("name", key)
     console.print(f"\n[green]✓[/green] Integration '{name}' upgraded successfully")