feat(core): declare module structure

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

crates/core/src/bookmark.rs

@@ -0,0 +1 @@
+pub struct BookmarkManager {/* TODO */}

crates/core/src/config.rs

@@ -0,0 +1 @@
+pub struct AppConfig {/* TODO */}

crates/core/src/filter.rs

@@ -0,0 +1 @@
+pub struct Filter {/* TODO */}

crates/core/src/io/file_reader.rs

@@ -0,0 +1,13 @@
+use crate::error::Result;
+use std::path::Path;
+
+pub struct FileReader {/* TODO */}
+
+impl FileReader {
+    pub fn open(_path: &Path) -> Result<Self> {
+        todo!()
+    }
+    pub fn file_size(&self) -> u64 {
+        todo!()
+    }
+}

crates/core/src/io/line_index.rs

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+pub struct LineIndex {/* TODO */}

crates/core/src/io/mod.rs

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+pub mod file_reader;
+pub mod line_index;

crates/core/src/lib.rs

@@ -1,10 +1,10 @@
+pub mod bookmark;
+pub mod config;
 pub mod error;
+pub mod filter;
+pub mod io;
+pub mod parser;
+pub mod search;
+pub mod session;
 pub mod types;
-// pub mod io; — Task 4
-// pub mod search; — Task 4
-// pub mod parser; — Task 4
-// pub mod watcher; — Task 4
-// pub mod filter; — Task 4
-// pub mod bookmark; — Task 4
-// pub mod config; — Task 4
-// pub mod session; — Task 4
+pub mod watcher;

crates/core/src/parser/json.rs

@@ -0,0 +1,8 @@
+use crate::types::LogEntry;
+
+pub fn parse_line(_line: &str) -> Option<LogEntry> {
+    todo!()
+}
+pub fn detect_json_log(_line: &str) -> bool {
+    todo!()
+}

crates/core/src/parser/mod.rs

@@ -0,0 +1 @@
+pub mod json;

crates/core/src/search/engine.rs

@@ -0,0 +1 @@
+pub struct SearchEngine {/* TODO */}

crates/core/src/search/mod.rs

@@ -0,0 +1 @@
+pub mod engine;

crates/core/src/session.rs

@@ -0,0 +1 @@
+pub struct SessionManager {/* TODO */}

crates/core/src/watcher/file_watcher.rs

@@ -0,0 +1,2 @@
+pub struct FileWatcher {/* TODO */}
+pub struct SmartFollow {/* TODO */}

crates/core/src/watcher/mod.rs

@@ -0,0 +1 @@
+pub mod file_watcher;