Fully support all mention kinds (#36134)

Feature parity with the agent1 @mention kinds:
- File
- Symbols
- Selections
- Threads
- Rules
- Fetch


Release Notes:

- N/A

---------

Co-authored-by: Cole Miller <cole@zed.dev>

crates/acp_thread/Cargo.toml

@@ -18,6 +18,7 @@ test-support = ["gpui/test-support", "project/test-support"]
 [dependencies]
 action_log.workspace = true
 agent-client-protocol.workspace = true
+agent.workspace = true
 anyhow.workspace = true
 buffer_diff.workspace = true
 collections.workspace = true
@@ -28,6 +29,7 @@ itertools.workspace = true
 language.workspace = true
 markdown.workspace = true
 project.workspace = true
+prompt_store.workspace = true
 serde.workspace = true
 serde_json.workspace = true
 settings.workspace = true