Agent PBX v0.3.0

Highlights

• Adds the corrected tmux-backed palette /plan flow: type /plan first, then send one Agent PBX planning prompt with structured plan-option instructions.
• Adds literal tmux key sending for slash commands so Codex handles them as interactive commands.
• Expands README guidance for palette commands and custom TUI theme creation.
• Bumps package version to 0.3.0 and modernizes Apache-2.0 package license metadata.

Verification

• python -m pytest: 169 passed
• git diff --check: passed
• Built dist/agent-pbx-wheelhouse.tar.gz
• Smoke installed from the local wheelhouse and verified agent-pbx --version reports 0.3.0