feat(channels): add channel-owned setup contracts (#112176)

* feat(channels): add channel-owned setup contracts

* test(channels): align legacy setup fixtures

* chore(channels): regenerate config and SDK baselines after rebase

* fix(update): run fresh doctor after current-process core changes

* fix(channels): align add pre-scan with execution precedence

* style(cli): format channels-cli test additions

* fix(channels): restore option-before-positional channel resolution via metadata arity scan

* fix(channels): keep help flags out of metadata arity escalation

* test(update): mock fresh post-update doctor in current-process suites

* style: format review fixes and correct entrypoint mock type

* fix(channels): register only modern contract options for dual-publishing plugins

* test(update): align downgrade suites with fresh-doctor child invocation

* docs(channels): record empty-contract and input-forwarding invariants

* fix(line): keep the shipped --token switch as a channel access token alias

* fix(signal): stop treating exact cross-family loopback endpoints as bind-aligned

* chore(config): regenerate docs config baselines after second rebase

* style: format rebased channels add tests

* fix(channels): enforce field-key and flag-name agreement in setup contracts

* fix(signal): detect container endpoints for bare --http-url setup

* fix(signal): ignore unconfigured accounts in transport collision checks

* fix(channels): validate negated setup flags in contract and normalizer

* fix(signal): preserve existing transport kind when setup detection is unreachable

* style(signal): use direct boolean check in collision guard

* style(signal): type test config literals

* docs(update): record two-read design of fresh-doctor validation gate

* fix(channels): satisfy post-rebase architecture gates

* docs: refresh channel setup map

---------

Co-authored-by: Peter Steinberger <steipete@gmail.com>

scripts/lib/official-external-channel-catalog.json

@@ -637,6 +637,10 @@
               "flags": "--signal-number <e164>",
               "description": "Signal account number (E.164)"
             },
+            {
+              "flags": "--signal-transport <kind>",
+              "description": "Signal HTTP transport (external-native or container)"
+            },
             {
               "flags": "--http-host <host>",
               "description": "Signal HTTP daemon host"

scripts/plugin-sdk-surface-report.mjs

@@ -146,8 +146,9 @@ export function readPluginSdkSurfaceBudgets(env = process.env) {
       // +4: session discussion state, info, provider, and registration contracts.
       // +2: structured media placeholder formatter and its text-fact contract.
       // +2: narrow settled-turn finalization result and safe full-attempt projector.
+      // +1: channel-owned setup contract factory.
       // +18: generic schema primitives needed by plugin-owned channel config schemas.
-      4695,
+      4696,
       env,
     ),
     publicFunctionExports: readPluginSdkSurfaceBudgetEnv(
@@ -155,8 +156,9 @@ export function readPluginSdkSurfaceBudgets(env = process.env) {
       // +1: session discussion provider registration.
       // +1: structured media placeholder formatter for text-only channel carriers.
       // +1: settled-turn full-attempt projector.
+      // +1: channel-owned setup contract factory.
       // +4: generic channel schema shape builders.
-      2845,
+      2846,
       env,
     ),
     publicDeprecatedExports: readPluginSdkSurfaceBudgetEnv(