refactor(craft): organize sandbox proxy modules and models (#15561)

docs/craft/dev/local-compose-craft.md

@@ -149,7 +149,7 @@ Iterate on `sandbox_proxy/` code with the VSCode debugger attached.
 
 4. **Provision a sandbox** via the API as you normally would, and
    trigger a gated action (e.g. a Slack `chat.postMessage`). Set
-   breakpoints in `gate.py`, `addons/gate.py`, `identity_docker.py`,
+   breakpoints in `gate.py`, `addons/gate.py`, `sandbox_identity/docker.py`,
    etc.
 
 ## Smoke-check commands

docs/craft/features/egress-proxy-and-approvals/README.md

@@ -20,15 +20,16 @@ The short version:
 
 Proxy runtime:
 
+- `backend/onyx/sandbox_proxy/models.py` defines shared destination, credential
+  injection, and MCP classification models.
 - `backend/onyx/sandbox_proxy/server.py` starts mitmproxy, health checks, CA
   bootstrap, identity lookup, request evaluator, credential resolvers, and the
   gate addon.
 - `backend/onyx/sandbox_proxy/addons/gate.py` owns request classification,
   approval parking, grant resolution, credential injection dispatch, internal
   destination blocking, and SIGTERM drain cleanup.
-- `backend/onyx/sandbox_proxy/identity.py`,
-  `identity_k8s.py`, and `identity_docker.py` resolve source IPs to sandbox,
-  tenant, and user identity.
+- `backend/onyx/sandbox_proxy/sandbox_identity/` modules resolve source IPs to sandbox,
+  tenant, and user identity. Its `models.py` defines the identity and session models.
 - `backend/onyx/sandbox_proxy/request_evaluator.py` turns mitmproxy requests
   into external-app action matches.
 - `backend/onyx/sandbox_proxy/credential_injection.py` and
@@ -36,7 +37,7 @@ Proxy runtime:
   and external-app credentials.
 - `backend/onyx/sandbox_proxy/approval_cache.py` defines Redis announce, wake,
   and session-grant cache keys.
-- `backend/onyx/sandbox_proxy/ca.py`, `ca_k8s.py`, and `ca_docker.py` manage
+- `backend/onyx/sandbox_proxy/certificate_authority/` modules manage
   the proxy CA.
 
 Approval persistence and API:

docs/craft/features/scheduled-tasks/pre-approvals.md

@@ -43,7 +43,7 @@ Constraints from the existing code that shape the design:
   actions with a stored `external_app_policy` row reach the matcher at
   all; "gated" means a stored row with `ASK`.
 - **`SessionContext` does not carry `origin`** —
-  `resolve_session_by_id` (`sandbox_proxy/identity.py`) selects only
+  `resolve_session_by_id` (`sandbox_proxy/sandbox_identity/resolution.py`) selects only
   `BuildSession.id`. The short-circuit needs one new joined lookup:
   `BuildSession → ScheduledTaskRun (session_id FK) → ScheduledTask`;
   grants come along with the task row.