feat(forge): pluggable forge abstraction + GitLab and Gitea/Forgejo/Codeberg (#1913)

* refactor(forge): forge-neutral foundation (GitHub-only)

Decouple git-hosting from GitHub behind a neutral abstraction (issue #1616), GitHub-only for now; existing GitHub behaviour is unchanged.

- Forge manifest, neutral ForgeService contract, forge registry + resolver, and a client forge-module registry.
- GitHub code renamed to the neutral shape; PR/Issue attachment wording preserved.
- forge.search.response enums parse tolerantly (unknown kind/auth state degrade instead of breaking the client).
- createPullRequest reports typed CLI/auth errors instead of a generic message.
- forge-resolver host/remote caches are LRU-bounded.
- Forge host trust is explicit: only a known cloud host or a CLI-authenticated host is ever talked to; an unauthenticated GitHub Enterprise host fails resolution instead of routing to github.com.
- Docs: forge-providers guide, glossary and i18n forge-copy conventions, architecture and rpc-namespacing terminology.
- Vitest React Native mocks (unistyles, svg, linking, lucide) consolidated into shared aliased test-stubs.

* feat(forge): GitLab adapter, forge-aware UI, pipelines and approvals

GitLab adapter over the glab CLI on the neutral contracts: MR status, forge-aware UI, pipeline tree, and N-of-M approvals.

- threadIsResolved is part of the neutral timeline item.
- Pipeline load failures show an error instead of an empty section.
- Manual pipeline jobs render as pending.
- Fork/detached MR head pipelines are fetched by MR iid (glab ci get --merge-request).

* feat(forge): Gitea family adapter (Gitea, Forgejo, Codeberg)

One adapter over the tea CLI serving Gitea, Forgejo, and Codeberg on the neutral contracts.

- CI status aggregates commit statuses and Actions runs together.
- Gitea's terminal "warning" state maps to failure on server and client.
- Gitea Actions check details are reachable from the PR pane by workflowRunId.

* refactor(forge): localize compatibility handling

* test(forge): expect normalized GitLab facts

---------

Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>

packages/app/src/git/merge-capability.ts

@@ -0,0 +1,51 @@
+import {
+  type ForgeSpecificEnvelope,
+  type LegacyGithubMergeFacts,
+  type MergeCapability,
+} from "@/git/client-forge-module";
+import { CLIENT_FORGE_LOGIC_MODULES } from "@/git/forges";
+
+export type ForgeSpecificStatusFacts = ForgeSpecificEnvelope;
+
+export type { LegacyGithubMergeFacts, MergeCapability };
+
+/**
+ * Resolve the neutral merge capability from a registered forge's runtime facts.
+ * Returns null for an unregistered, unknown, or schema-mismatched facts family;
+ * callers then fall back to raw git state.
+ */
+function deriveForgeMergeCapability(facts: unknown): MergeCapability | null {
+  for (const module of CLIENT_FORGE_LOGIC_MODULES) {
+    const capability = module.facts?.deriveMergeCapability(facts);
+    if (capability) {
+      return capability;
+    }
+  }
+  return null;
+}
+
+/**
+ * Build the neutral merge capability from a forge's PR status facts. Returns
+ * null when the forge supplied no merge facts (e.g. a host that exposes none, or
+ * an unknown forge), in which case the caller falls back to raw git state.
+ * Per-forge derivation lives on client forge modules; this stays the single
+ * neutral entry point the action policy reads.
+ *
+ * COMPAT(forgeSpecific): added in v0.1.106, remove after 2026-12-27. A daemon
+ * predating forgeSpecific emits only the legacy `status.github` field. When
+ * forgeSpecific is absent we synthesize the github arm from those legacy facts
+ * so GitHub merge-method restrictions and auto-merge state are not lost against
+ * an old daemon.
+ */
+export function deriveMergeCapability(
+  forgeSpecific: unknown,
+  legacyGithubFacts?: LegacyGithubMergeFacts | null,
+): MergeCapability | null {
+  if (forgeSpecific === null || forgeSpecific === undefined) {
+    if (legacyGithubFacts) {
+      return deriveForgeMergeCapability({ forge: "github", ...legacyGithubFacts });
+    }
+    return null;
+  }
+  return deriveForgeMergeCapability(forgeSpecific);
+}