docs: tambah doc comment, logging, dan inline comments di semua 255 file

Meliputi:
- File-level //! doc comment: tujuan file, alur kerja, komponen utama
- Function-level /// doc comment: apa, parameter, return, flow, edge cases
- Struct/enum/trait /// doc comment: peran, field docs
- Tracing logging (tracing::info!/debug!/trace!/warn!/error!) di setiap fungsi
- Inline comments untuk variable dan branching logic penting
- Seluruh 8 crates di workspace: zesdex-backend, zesdex-cms, zesdex-entities,
  zesdex-iam, zesdex-infra, zesdex-ipc, zesdex-middleware, zesdex-utils
- Build: 0 errors, 242/242 tests passed

crates/zesdex-backend/src/app/mode/mod.rs

@@ -1,16 +1,19 @@
 //! TUI mode definitions and per-mode input/action handlers, one submodule
 //! per overlay/mode (bash, editor, effort, mcp, quit confirm, rewind, etc.).
-pub mod bash;
-pub mod editor;
-pub mod effort;
-pub mod key_input;
-pub mod mcp;
+//! Each mode encapsulates its own keyboard input parsing, state transitions,
+//! and view rendering so the top-level event loop can dispatch generically.
 
-pub mod learning;
-pub mod quit_confirm;
-pub mod rewind;
-pub mod settings;
-pub mod todo;
+pub mod bash;         // Shell-command input overlay: prompt, history, execution
+pub mod editor;       // Multi-line text editor overlay (write/edit tool content)
+pub mod effort;       // Reasoning-effort selector overlay
+pub mod key_input;    // Generic single-key prompt overlay (e.g. rename, search)
+pub mod mcp;          // MCP tool argument builder overlay
+
+pub mod learning;     // Learning/reflection input overlay
+pub mod quit_confirm; // Quit confirmation dialog overlay
+pub mod rewind;       // Rewind/undo checkpoint selection overlay
+pub mod settings;     // Settings panel overlay
+pub mod todo;         // TODO-list management overlay
 
 /// Cycle `current` in the range `[0, len)`.
 ///