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>

docs/i18n.md

@@ -37,6 +37,15 @@ npx vitest run packages/app/src/i18n/resources.test.ts --bail=1
 
 The parity test catches missing keys across English and every supported locale resource.
 
+## Forge-Variant Copy
+
+Strings that vary by git forge follow a two-tier rule:
+
+- **Indeclinable tokens** — brand names ("GitHub", "GitLab"), the PR/MR initialism, number prefixes (`#`/`!`) — are interpolated into a single key (`"Refresh git and {{brand}} state"`). These tokens stay latin and uninflected in every supported locale, so one string per locale suffices. The value comes from the forge manifest via `getForgePresentation`.
+- **Sentences containing the full change-request noun** ("pull request" / "merge request" inflects and takes gender/case in translation) use the i18next `context` mechanism: the base key carries the pull-request wording and an `_mr` sibling carries the merge-request wording (`pullRequest` / `pullRequest_mr`). Call sites pass `t(key, { context: getForgePresentation(forge).changeRequestContext })`; an undefined or unknown context falls back to the base key.
+
+Keys scale per vocabulary family (PR vs MR), not per forge: a new forge picks an existing family in its manifest entry and needs zero locale edits.
+
 ## Migration Order
 
 Client UI translation is staged so each pass can migrate complete local copy clusters and keep reviews focused.