Fix GitLab::getEvent() field/action parity with Gitea's shape

[HarshMN2345]

Summary

GitLab's getEvent() (added in #118, feat/appwrite-provider-parity) returns push/merge_request event data in a shape that doesn't match Gitea's or GitHub's -- consumers relying on the common field contract (e.g. Appwrite's VCS integration) would silently drop every event.

Verified against real GitLab webhook payload structure:

• Missing repositoryId entirely -- any DB lookup keyed on it finds nothing.
• Non-standard key names: name/commitAuthor/commitMessage/commitUrl instead of repositoryName/headCommitAuthorName/headCommitMessage/headCommitUrl (matching Gitea's/GitHub's convention).
• Merge request action passed through raw GitLab values (open/reopen/update/close) instead of the GitHub/Gitea convention (opened/reopened/synchronize/closed) consumers already branch on. Also maps GitLab's distinct merge action to closed, since a merged MR is done either way.
• Also adds repositoryUrl, branchUrl, affectedFiles, branch create/delete detection, and cross-project (fork) detection for external MRs -- all present in Gitea's return shape but missing from GitLab's.

While integrating against a real GitLab OAuth app end-to-end (not just mocked HTTP), three further real bugs surfaced -- all fixed here too:

• Wrong auth header for OAuth2 tokens. The adapter authenticated every request with PRIVATE-TOKEN: <token> (and ?private_token= for presigned URLs), which is only valid for GitLab Personal Access Tokens. Our integration uses OAuth2 access tokens, which GitLab requires as Authorization: Bearer <token>. Every API call was failing with 401 "Bad credentials" regardless of token freshness.
• searchRepositories() dropped private repos in personal namespaces. The personal-namespace fallback called GET /users/{username}/projects, which GitLab only returns public projects for, even for the authenticated user's own account. Switched to GET /projects?membership=true (every project -- public and private -- the token's user is a member of) with client-side filtering by namespace.path.
• searchRepositories() return shape didn't match GitHub/Gitea's items/total contract. It returned a bare indexed array instead of ['items' => [...], 'total' => N], breaking any consumer destructuring the common shape. total is now taken from the X-Total response header (or the filtered count, when the personal-namespace client-side filter is in effect, since the header reflects all namespaces in that case).

Test plan

• Updated testGetEventPush/testGetEventPullRequest to assert the corrected shape
• New testGetEventPullRequestActionMapping covers all 5 native action values
• New testGetEventPullRequestDetectsExternal covers fork/cross-project MR detection
• New testGetEventPushDetectsBranchCreated/testGetEventPushDetectsBranchDeleted
• Updated testSearchRepositories/testSearchRepositoriesWithSearch to assert against the new items/total shape
• composer format/composer check (PHPStan level 8) clean
• Verified live end-to-end against a real GitLab OAuth app and repository (auth header + searchRepositories fixes were only caught this way -- unit tests use mocked HTTP and couldn't have caught either)

[greptile-apps]

Greptile Summary

This PR fixes GitLab::getEvent() so its push and merge-request return shapes match Gitea's established contract, and simultaneously migrates all API calls from the PRIVATE-TOKEN header to Authorization: Bearer while updating searchRepositories() to return {items, total} (matching the GitHub adapter's shape).

• getEvent() field parity: Renames name/commitAuthor/commitMessage/commitUrl to repositoryName/headCommitAuthorName/headCommitMessage/headCommitUrl; adds repositoryId, repositoryUrl, branchUrl, affectedFiles, branchCreated, branchDeleted, and external; maps GitLab's native MR actions (open/reopen/update/close/merge) to the GitHub/Gitea verbs consumers already branch on.
• Auth header migration: All PRIVATE-TOKEN request headers are replaced with Authorization: Bearer, and the archive download URL switches from private_token to access_token.
• Test coverage: New dedicated tests cover branch-create detection, branch-delete detection, all five MR action mappings, and cross-project (fork) MR detection.

Confidence Score: 5/5

Safe to merge — the changes are well-scoped field renames and additions with matching test coverage for every new code path.

The getEvent() return shapes align precisely with Gitea's adapter, the action-mapping constant is correct, the zero-SHA sentinel for branch create/delete is the standard GitLab convention, and searchRepositories() now matches the GitHub adapter's {items, total} structure. No logic paths were left untested by the new test methods.

No files require special attention.

Important Files Changed

Filename	Overview
src/VCS/Adapter/Git/GitLab.php	Reworks getEvent() to produce a return shape that matches Gitea's adapter exactly (repositoryId, repositoryName, repositoryUrl, headCommit* keys, affectedFiles, branchCreated/branchDeleted, action mapping); also migrates all API calls from PRIVATE-TOKEN header to Authorization: Bearer, updates archive URL parameter to access_token, and changes searchRepositories() to return {items, total} matching GitHub's shape.
tests/VCS/Adapter/GitLabTest.php	Updates getEvent push/MR tests to assert the corrected field names; adds testGetEventPushDetectsBranchCreated, testGetEventPushDetectsBranchDeleted, testGetEventPullRequestActionMapping, and testGetEventPullRequestDetectsExternal; updates searchRepositories assertions for the new {items, total} return shape.

_{Reviews (5): Last reviewed commit: "Fix searchRepositories() return shape to..." | Re-trigger Greptile}