Release v0.4.0

Highlights

• Builtin extension abstraction — New public Extension trait groups related builtins for one-call registration on BashBuilder/BashToolBuilder. TypeScript registration now flows through TypeScriptExtension, and ScriptedTool reuses a shared ToolDefExtension for its per-call logic shell (#1515, #1518).
• Clap-backed custom builtins — Custom builtins can now be defined declaratively against a clap parser, replacing hand-rolled arg parsing for new integrations (#1514).
• SQLite session engine cache — The sqlite builtin keeps a session-scoped engine alive across exec() calls, so transactions and prepared state survive multiple shell invocations within one session (#1513).
• SQLite hardening follow-up — PRAGMA policy parsing now handles SQL comments and quoted/bracket/backtick identifiers (closing a PRAGMA main."cache_size" bypass), and max_db_bytes is enforced consistently across VFS writes/truncates and memory-backend persistence (#1521).
• Python + toolchain bumps — Embedded Python (monty) bumped to 0.0.17 and Rust toolchain bumped to 1.95.0 across rust-toolchain.toml and matching CI workflow refs (#1520).

What's Changed

• bench(sqlite): add Criterion benchmark for sqlite builtin (#1523) by @chaliy
• chore(python): bump monty to 49faa4c (0.0.17) and Rust to 1.95.0 (#1520) by @chaliy
• fix(deps): bump postcss to 8.5.13 in browser example (#1522) by @chaliy
• fix(sqlite): harden pragma policy and db caps (#1521) by @chaliy
• test(ssh): retry live supabase smoke (#1519) by @chaliy
• feat(scripted-tool): add ToolDef extension (#1518) by @chaliy
• feat(sqlite): session-scoped engine cache for transactions across exec() (#1513) by @chaliy
• feat(extension): add builtin extension abstraction (#1515) by @chaliy
• feat(builtins): support clap-backed custom builtins (#1514) by @chaliy
• test(sqlite): add differential tests vs host sqlite3 binary (#1511) by @chaliy

Full Changelog: v0.3.0...v0.4.0