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/flags.rs

@@ -21,6 +21,7 @@ pub struct Flags {
     pub allow_file_access: bool,
     pub device: Option<String>,
     pub auto_connect: bool,
+    pub session_name: Option<String>,
 
     // Track which launch-time options were explicitly passed via CLI
     // (as opposed to being set only via environment variables)
@@ -67,6 +68,7 @@ pub fn parse_flags(args: &[String]) -> Flags {
         allow_file_access: env::var("AGENT_BROWSER_ALLOW_FILE_ACCESS").is_ok(),
         device: env::var("AGENT_BROWSER_IOS_DEVICE").ok(),
         auto_connect: env::var("AGENT_BROWSER_AUTO_CONNECT").is_ok(),
+        session_name: env::var("AGENT_BROWSER_SESSION_NAME").ok(),
         // Track CLI-passed flags (default false, set to true when flag is passed)
         cli_executable_path: false,
         cli_extensions: false,
@@ -178,6 +180,12 @@ pub fn parse_flags(args: &[String]) -> Flags {
                 }
             }
             "--auto-connect" => flags.auto_connect = true,
+            "--session-name" => {
+                if let Some(s) = args.get(i + 1) {
+                    flags.session_name = Some(s.clone());
+                    i += 1;
+                }
+            }
             _ => {}
         }
         i += 1;
@@ -215,6 +223,7 @@ pub fn clean_args(args: &[String]) -> Vec<String> {
         "-p",
         "--provider",
         "--device",
+        "--session-name",
     ];
 
     for arg in args.iter() {