fix(dolt): resolve shared-server CLI dir from shared root

[s-a-c]

Summary

In shared-server mode, CLIDir() can resolve from the authoritative shared Dolt root instead of the per-project .beads/dolt/<db> path.

This change is intentionally limited to shared-server mode. It does not change generic external-server behavior.

What changed

• update internal/storage/dolt/store.go
  • when serverMode is true and IsSharedServerMode() is true, resolve CLIDir() via doltserver.ResolveDoltDir(beadsDir)
  • preserve the old dbPath behavior everywhere else
• add direct path-resolution coverage in internal/storage/dolt/open_test.go
• add shared-server routing-guard coverage in internal/storage/dolt/credentials_test.go
• add a workflow-style integration regression in internal/storage/dolt/git_remote_shared_server_test.go

Why this scope

Shared-server mode has a local, authoritative Dolt root. Generic external-server mode does not necessarily have that property, so this PR avoids changing that behavior.

The goal here is to fix the shared-server CLI path case without claiming to solve the broader external-server path-authority problem.

Verification

• CGO_ENABLED=0 go test ./internal/storage/dolt -run 'TestCLIDirUsesSharedDoltRootInSharedServerMode|TestCLIDirUsesDbPathOutsideSharedServerMode|TestCredentialCLIRoutingSharedServerUsesSharedDoltRoot|TestCloudAuthCLIRoutingSharedServerUsesSharedDoltRoot'
• CGO_ENABLED=0 go test -count=1 -tags integration ./internal/storage/dolt -run 'TestCredentialCLIRoutingE2ESharedServer|TestCredentialCLIRoutingE2E|TestGitRemoteExternalServerRouting'

Both passed in a clean branch containing only this scoped slice.

Closes #3219

[Copilot]

Pull request overview

This PR fixes how DoltStore.CLIDir() resolves the working directory for dolt CLI subprocesses in shared-server mode by deriving the path from the authoritative shared Dolt root (instead of the per-project .beads/dolt/<db> layout). This aligns CLI-based operations (e.g., remote, push, pull) with where the shared server actually stores database repos.

Changes:

• Update DoltStore.CLIDir() to resolve from doltserver.ResolveDoltDir(beadsDir) when serverMode + shared-server mode are enabled.
• Add unit coverage for shared-server vs non-shared-server CLIDir() resolution.
• Add routing/guard tests and an integration regression test validating shared-server credential-bearing CLI routing through the shared Dolt root.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
internal/storage/dolt/store.go	Adjusts CLIDir() to use the shared Dolt root for shared-server mode, preserving legacy behavior elsewhere.
internal/storage/dolt/open_test.go	Adds direct tests asserting CLIDir() path resolution in shared-server vs non-shared-server mode.
internal/storage/dolt/credentials_test.go	Adds tests ensuring credential/cloud-auth CLI routing resolves remotes via the shared Dolt root in shared-server mode.
internal/storage/dolt/git_remote_shared_server_test.go	Adds an integration test proving end-to-end shared-server credential routing succeeds even when the per-project CLI dir is stale.