Add paste summarization to Codex TUI (#1549)

## Summary
- introduce `Paste` event to avoid per-character paste handling
- collapse large pasted blocks to `[Pasted Content X lines]`
- store the real text so submission still includes it
- wire paste handling through `App`, `ChatWidget`, `BottomPane`, and
`ChatComposer`

## Testing
- `cargo test -p codex-tui`


------
https://chatgpt.com/codex/tasks/task_i_6871e24abf80832184d1f3ca0c61a5ee


https://github.com/user-attachments/assets/eda7412f-da30-4474-9f7c-96b49d48fbf8

codex-rs/Cargo.lock

@@ -787,6 +787,7 @@ dependencies = [
  "color-eyre",
  "crossterm",
  "image",
+ "insta",
  "lazy_static",
  "mcp-types",
  "path-clean",
@@ -871,6 +872,18 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "console"
+version = "0.15.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "054ccb5b10f9f2cbf51eb355ca1d05c2d279ce1804688d0db74b4733a5aeafd8"
+dependencies = [
+ "encode_unicode",
+ "libc",
+ "once_cell",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "convert_case"
 version = "0.6.0"
@@ -1230,6 +1243,12 @@ dependencies = [
  "log",
 ]
 
+[[package]]
+name = "encode_unicode"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34aa73646ffb006b8f5147f3dc182bd4bcb190227ce861fc4a4844bf8e3cb2c0"
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.35"
@@ -2110,6 +2129,17 @@ version = "2.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f4c7245a08504955605670dbf141fceab975f15ca21570696aebe9d2e71576bd"
 
+[[package]]
+name = "insta"
+version = "1.43.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "154934ea70c58054b556dd430b99a98c2a7ff5309ac9891597e339b5c28f4371"
+dependencies = [
+ "console",
+ "once_cell",
+ "similar",
+]
+
 [[package]]
 name = "instability"
 version = "0.3.7"