Flatten proxy config to a bool (drop the caddy key)

CaddySpec had only `enable` left (path_prefix/host removed; extra_snippets was
unused), so `proxy: { caddy: {} }` was three levels of nesting for a checkbox —
and it invited drift (supabase silently reverted to proxy.caddy.host). Replace it
with a plain `ServiceSpec.proxy: bool`.

- Model: remove ProxySpec/CaddySpec; `proxy: bool = False`. Readers simplified to
  `bool(svc.proxy)` (generator, castle-api summaries, CLI info).
- CLI create / dashboard editor + create form: write `proxy: true` / a checkbox.
- Configs migrated to `proxy: true` (and supabase's stale proxy.caddy.host block
  removed).
- Docs (registry, dns-and-tls, design, stack guides) + tests/fixtures updated;
  also fixed lingering path-model staleness in the stack guides.

cli/src/castle_cli/commands/create.py

@@ -8,14 +8,12 @@ import subprocess
 from castle_cli.config import REPOS_DIR, load_config, save_config
 from castle_cli.manifest import (
     BuildSpec,
-    CaddySpec,
     DefaultsSpec,
     ExposeSpec,
     HttpExposeSpec,
     HttpInternal,
     ManageSpec,
     ProgramSpec,
-    ProxySpec,
     RunPython,
     ServiceSpec,
     SystemdSpec,
@@ -121,7 +119,7 @@ def run_create(args: argparse.Namespace) -> int:
                     health_path="/health",
                 )
             ),
-            proxy=ProxySpec(caddy=CaddySpec()),  # expose at <name>.<gateway.domain>
+            proxy=True,  # expose at <name>.<gateway.domain>
             manage=ManageSpec(systemd=SystemdSpec()),
             # python-fastapi scaffold reads env_prefix MY_SERVICE_ — map castle's
             # computed port/data dir to those vars (explicit, no hidden injection).

cli/src/castle_cli/commands/deploy_create.py

@@ -11,14 +11,12 @@ import argparse
 
 from castle_cli.config import load_config, save_config
 from castle_cli.manifest import (
-    CaddySpec,
     DefaultsSpec,
     ExposeSpec,
     HttpExposeSpec,
     HttpInternal,
     JobSpec,
     ManageSpec,
-    ProxySpec,
     RunCommand,
     RunPython,
     ServiceSpec,
@@ -62,7 +60,7 @@ def run_service_create(args: argparse.Namespace) -> int:
     run = _run_spec(args.runner, args.run or args.program or name, name)
 
     expose = None
-    proxy = None
+    proxy = False
     if args.port is not None:
         expose = ExposeSpec(
             http=HttpExposeSpec(
@@ -70,9 +68,8 @@ def run_service_create(args: argparse.Namespace) -> int:
                 health_path=args.health,
             )
         )
-        if not args.no_proxy:
-            # Expose at <name>.<gateway.domain> (the subdomain is the service name).
-            proxy = ProxySpec(caddy=CaddySpec())
+        # Expose at <name>.<gateway.domain> (the subdomain is the service name).
+        proxy = not args.no_proxy
 
     config.services[name] = ServiceSpec(
         id=name,
@@ -90,7 +87,7 @@ def run_service_create(args: argparse.Namespace) -> int:
     print(f"  runs:   {args.runner} ({args.run or args.program or name})")
     if expose:
         print(f"  port:   {args.port}")
-    if proxy and proxy.caddy:
+    if proxy:
         print(f"  subdomain: {name}.<gateway.domain>")
     print(f"\nNext: castle service deploy {name} && castle service start {name}")
     return 0

cli/src/castle_cli/commands/info.py

@@ -119,7 +119,7 @@ def run_info(args: argparse.Namespace) -> int:
             print(f"  {BOLD}port{RESET}:        {http.internal.port}")
             if http.health_path:
                 print(f"  {BOLD}health{RESET}:      {http.health_path}")
-        if service.proxy and service.proxy.caddy and service.proxy.caddy.enable:
+        if service.proxy:
             print(f"  {BOLD}subdomain{RESET}:   {name}.<gateway.domain>")
         if service.manage and service.manage.systemd:
             sd = service.manage.systemd

cli/src/castle_cli/manifest.py

@@ -3,7 +3,6 @@
 from castle_core.manifest import *  # noqa: F401, F403
 from castle_core.manifest import (  # noqa: F401 — explicit re-exports for type checkers
     BuildSpec,
-    CaddySpec,
     Capability,
     CommandsSpec,
     DefaultsSpec,
@@ -15,7 +14,6 @@ from castle_core.manifest import (  # noqa: F401 — explicit re-exports for typ
     JobSpec,
     ManageSpec,
     ProgramSpec,
-    ProxySpec,
     ReadinessHttpGet,
     RestartPolicy,
     RunBase,