feat: add session persistence, state management commands, and --new-tab click (#184)

Rebased and fixed implementation of PR #184 features on current main:

Session persistence:
- --session-name flag and AGENT_BROWSER_SESSION_NAME env var auto-save/restore
  cookies and localStorage across browser restarts
- State files stored in ~/.agent-browser/sessions/ with owner-only permissions
- AES-256-GCM encryption via AGENT_BROWSER_ENCRYPTION_KEY env var
- Auto-expiration of old state files (AGENT_BROWSER_STATE_EXPIRE_DAYS, default 30)

State management commands:
- state list: list saved state files with metadata
- state show <file>: display state summary (cookies, origins, domains)
- state rename <old> <new>: rename state files
- state clear [name] [--all]: clear saved states
- state clean --older-than <days>: delete expired states

New --new-tab flag for click command:
- Opens link href in a new tab instead of navigating the current tab

Security hardening:
- Session name validation prevents path traversal (CLI + daemon)
- safeHeaderMerge prevents prototype pollution in header merging
- WebSocket stream server binds to 127.0.0.1 only
- State files written with 0o600 permissions

Fixes applied over the original PR:
- Use color.rs module instead of hardcoded ANSI escape codes
- Align CLI output field names with daemon response format
- Add CLI-level --session-name validation (not just daemon-side)
- Avoid adding "DOM" to tsconfig.json lib (use proper typing in evaluate)
- Keep version at 0.9.3 (matches current main)
- Centralize session name validation in daemon.ts helper
- Update all documentation (README, SKILL.md, docs site, --help output)

Co-authored-by: Chris Tate <chris@ctate.dev>

cli/src/main.rs

@@ -4,6 +4,7 @@ mod connection;
 mod flags;
 mod install;
 mod output;
+mod validation;
 
 use serde_json::json;
 use std::env;
@@ -179,6 +180,7 @@ fn main() {
                     ParseError::UnknownSubcommand { .. } => "unknown_subcommand",
                     ParseError::MissingArguments { .. } => "missing_arguments",
                     ParseError::InvalidValue { .. } => "invalid_value",
+                    ParseError::InvalidSessionName { .. } => "invalid_session_name",
                 };
                 println!(
                     r#"{{"success":false,"error":"{}","type":"{}"}}"#,
@@ -192,6 +194,22 @@ fn main() {
         }
     };
 
+    // Validate session name before starting daemon
+    if let Some(ref name) = flags.session_name {
+        if !validation::is_valid_session_name(name) {
+            let msg = validation::session_name_error(name);
+            if flags.json {
+                println!(
+                    r#"{{"success":false,"error":"{}","type":"invalid_session_name"}}"#,
+                    msg.replace('"', "\\\"")
+                );
+            } else {
+                eprintln!("{} {}", color::error_indicator(), msg);
+            }
+            exit(1);
+        }
+    }
+
     let daemon_result = match ensure_daemon(
         &flags.session,
         flags.headed,
@@ -207,6 +225,7 @@ fn main() {
         flags.state.as_deref(),
         flags.provider.as_deref(),
         flags.device.as_deref(),
+        flags.session_name.as_deref(),
     ) {
         Ok(result) => result,
         Err(e) => {