enable-resume (#3537)

Adding the ability to resume conversations.
we have one verb `resume`. 

Behavior:

`tui`:
`codex resume`: opens session picker
`codex resume --last`: continue last message
`codex resume <session id>`: continue conversation with `session id`

`exec`:
`codex resume --last`: continue last conversation
`codex resume <session id>`: continue conversation with `session id`

Implementation:
- I added a function to find the path in `~/.codex/sessions/` with a
`UUID`. This is helpful in resuming with session id.
- Added the above mentioned flags
- Added lots of testing

codex-rs/core/Cargo.toml

@@ -19,6 +19,7 @@ base64 = "0.22"
 bytes = "1.10.1"
 chrono = { version = "0.4", features = ["serde"] }
 codex-apply-patch = { path = "../apply-patch" }
+codex-file-search = { path = "../file-search" }
 codex-mcp-client = { path = "../mcp-client" }
 codex-protocol = { path = "../protocol" }
 dirs = "6"