docs: adopt MIT license

[fly1d]

Summary

• add the standard MIT License with copyright 2026 fly1d
• align npm and Cargo package metadata with SPDX identifier MIT
• add an MIT badge and license section to the README

Verification

• npm run check (10 tests passed)
• npm run test:smoke (5 passed, 1 environment-specific test skipped)
• npm run desktop:check (2 Rust tests passed)
• npm and Cargo metadata both report MIT
• git diff --check

[fly1d]

Reviewed the complete licensing diff. LICENSE contains the full MIT grant, notice-retention condition, and warranty/liability disclaimer with copyright 2026 fly1d. npm and Cargo metadata both use the SPDX identifier MIT, the README links to the license, all five required GitHub checks pass, and the full local check suite passed. No blocking findings.