fix(tui): support image steering and immediate paste feedback

[daviddanialy]

Summary

• Fix image steering rejected by ACP's 256 KiB pending-injection budget: pin only agentkit-acp to the immutable media-budget fix in daviddanialy/agentkit at 6d519ed1e93e28e54ba1cc18889534e2e8337181.
• Account inline image/audio/blob payloads separately with a bounded 28 MiB serialized media budget; retain the 256 KiB non-media budget and aggregate/in-flight accounting.
• Show immediate [Pasting… #N] markers while clipboard work runs. Replace each marker at its original position, preserve cursor and FIFO ordering, and support cancellation by deletion or Escape without reviving late results. Enter waits for pending paste completion; editing cancels deferred submission.

Dependency review

• Verified the published fork branch resolves to the full pinned SHA, directly based on the previous Kit AgentKit revision 8e4ee26434a3f847e3613da5bb073ae63a262243.
• Current main has advanced to AgentKit bec9dcc45ee0f436d538286bc220b16dc19fd5f3. Its ACP source is unchanged from the fork's parent. Keep agentkit-loop 0.10.12 on main's existing upstream revision and redirect fork-local core/tools dependencies to existing registry packages; do not downgrade the loop or vendor the library.
• Lockfile delta changes only the ACP source: no new package versions, features, build scripts, unsafe code, or executable hooks. Existing feature selection is preserved.
• Residual provenance risk: the user-fork commit is unsigned. cargo audit is not installed, so an advisory scan was not run. The immutable pin and source-diff review do not constitute a signature or advisory audit.

Validation

• RUST_TEST_THREADS=1 mise run test -- --lib clipboard: 16 passed.
• RUST_TEST_THREADS=1 mise run test -- --lib tui::: 486 passed, 1 ignored.
• mise run build (cargo build --locked --bin kit) passed.
• mise run lint passed: formatting plus all-target/all-feature and no-default-feature Clippy with warnings denied.
• Locked reverse-dependency and feature inspection; git diff --check passed.
• Independent read-only review approved clipboard cancellation, stale-generation routing, cursor behavior, queued submission, and dependency redirects.

Scope

Exactly five files: Cargo.toml, Cargo.lock, src/tui/app.rs, src/tui/editor.rs, src/tui/mod.rs. Prepared in an isolated worktree from Kit main; unrelated original-worktree TUI edits are excluded. No release-version change.

[daviddanialy]

@kit-code-agent please restart the review of the latest commit. The previous run (D4681DC7-C451-4176-A521-0CB78FCD0565) appears stuck with its Reviewing status unchanged for over an hour.

[kit-code-agent]

History navigation can leave a pending clipboard marker untracked, discard the clipboard result, and restore the literal marker as submit-ready prompt text.

[kit-code-agent]

No issues found. The changes look good to merge.

[kit-code-agent]

No issues found. The changes look good to merge.