feat(egress-proxy): drive claude-code OAuth placeholder off a role marker

The chunk 2 detection keyed on `token_ref == "CLAUDE_CODE_OAUTH_TOKEN"`,
which broke any bottle whose host env var has a different name (e.g.
`CLAUDE_BOTTLE_OAUTH_TOKEN`). The token_ref is the user's choice —
the placeholder-env trigger shouldn't be locked to one specific
string.

Restoring a minimal `role` marker on `EgressProxyRoute`:

  - `EGRESS_PROXY_ROLES = frozenset({"claude_code_oauth"})` — one
    marker for now; the field is back so we can grow it.
  - `EGRESS_PROXY_SINGLETON_ROLES` — claude_code_oauth is a
    singleton (only one route per bottle can carry it).
  - `Role: tuple[str, ...]` field on `EgressProxyRoute` (manifest +
    runtime), parsed as string or list-of-strings; unknown roles
    are rejected so typos can't become silent no-ops.

`prepare.py:has_anthropic_auth` now checks for `"claude_code_oauth"
in r.roles` instead of matching a literal token_ref string. Bottles
can name their host OAuth env var anything; the role marker is what
flips on `CLAUDE_CODE_OAUTH_TOKEN=<placeholder>` and the
telemetry-off env vars on the agent.

Test coverage: 7 new manifest tests (omitted / string / list /
unknown role rejected / non-string rejected / list-item non-string
rejected / singleton enforced).

364 tests pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

claude_bottle/egress_proxy.py

@@ -62,13 +62,18 @@ class EgressProxyRoute:
     (e.g. `EGRESS_PROXY_TOKEN_0`); `token_ref` is the host env var
     the CLI reads at launch and forwards into the container's environ
     under `token_env`. Routes that share a `token_ref` coalesce to
-    one `token_env` slot."""
+    one `token_env` slot.
+
+    `roles` carries the manifest route's optional role markers (see
+    `manifest.EGRESS_PROXY_ROLES`). The launch step reads these for
+    side effects like the claude-code OAuth placeholder env."""
 
     host: str
     path_allowlist: tuple[str, ...] = ()
     auth_scheme: str = ""
     token_env: str = ""
     token_ref: str = ""
+    roles: tuple[str, ...] = ()
 
 
 @dataclass(frozen=True)
@@ -148,11 +153,13 @@ def egress_proxy_routes_for_bottle(
                 auth_scheme=r.AuthScheme,
                 token_env=token_env,
                 token_ref=r.TokenRef,
+                roles=r.Role,
             ))
         else:
             out.append(EgressProxyRoute(
                 host=r.Host,
                 path_allowlist=r.PathAllowlist,
+                roles=r.Role,
             ))
     return tuple(out)