Use getEntityId with resolveAsCell

[bfollington]

Summary by cubic

Fix getEntityId to return the underlying entity’s ID for Cells with paths (e.g., array items via .key(i)) instead of a path-based composite. This removes ID mismatches and simplifies mention resolution in the code editor.

• Bug Fixes
  • getEntityId now dereferences Cells with non-empty paths and uses the inner entity ID when present; falls back to path-based ID otherwise.
  • Added tests covering arrays of Cells accessed via .key() to ensure IDs match the underlying items.
  • Simplified CTCodeEditor mention lookup to rely on the consistent ID from getEntityId.

[cubic-dev-ai]

No issues found across 3 files

[seefeldb]

#1916 adds .resolveAsCell(), which should make the ct-code-editor change simpler, just call that on cells before call getEntityId.