fix: fall back to name lookup for UUID-shaped workspace names (#24340)

`namedWorkspace` in `cli/root.go` parsed workspace identifiers with
`uuid.Parse` first and returned immediately on success, even when no
workspace had that UUID as its actual ID. This caused 404 errors for any
workspace whose name was a valid 32-char hex string (dashless UUID).

- Add `codersdk.ResolveWorkspace`: tries UUID lookup first, falls back
to name lookup on 404. `NameValid` guard skips the fallback for standard
dashed UUIDs (36 chars > 32-char name limit).
- Export `codersdk.SplitWorkspaceIdentifier`, replacing the duplicate
`splitNamedWorkspace` in `cli/root.go` (uses `strings.Cut`).
- Delete `namedWorkspace` from `cli/root.go`; all 28 call sites now use
`client.ResolveWorkspace` directly.
- Delete `namedWorkspace` and `splitNameAndOwner` from
`codersdk/toolsdk/bash.go`; inline `client.ResolveWorkspace`.
- Simplify `GetWorkspace` tool handler to a single `ResolveWorkspace`
call.
- Unit tests via httptest mock cover UUID, name, owner/name, UUID-like
fallback, not-found, server error, transport error, and invalid
identifier paths.
- Integration tests in `cli/show_test.go` and `codersdk/toolsdk` for
workspaces with UUID-like names.

> Generated with Coder Agents

cli/exp_agents.go

@@ -131,7 +131,7 @@ func (r *RootCmd) agentsCommand() *serpent.Command {
 
 			var workspaceID *uuid.UUID
 			if workspaceFlag != "" {
-				workspace, err := namedWorkspace(inv.Context(), client, workspaceFlag)
+				workspace, err := client.ResolveWorkspace(inv.Context(), workspaceFlag)
 				if err != nil {
 					return xerrors.Errorf("resolve workspace %q: %w", workspaceFlag, err)
 				}