Migrate license from Apache-2.0 to MIT

[pentaxis93]

Context

agentd is Apache-2.0 but the Apache machinery — patent grants, NOTICE propagation, explicit contribution terms — serves multi-contributor corporate projects with patentable technology. agentd is a single-contributor agent daemon where none of that applies.

Migrating to MIT aligns with groundwork (see pentaxis93/groundwork#6) and Superpowers (already MIT), giving license uniformity across the full stack.

Change

• Replace LICENSE contents with MIT license text
• Update Cargo.toml license field(s) from Apache-2.0 to MIT
• Update any SPDX-License-Identifier headers if present

Acceptance criteria

• LICENSE contains MIT text with correct copyright
• All Cargo.toml files specify license = "MIT"
• No "Apache" references remain in project metadata
• Tests pass

[pentaxis93]

Implemented and merged in PR #18 (commit 7cd0f3e). Closing as complete.