fix: biome complexity lint failures blocking CI on dev

[namastex888]

Bug

CI on dev is failing due to biome cognitive complexity lint errors in two functions:

1. src/lib/provider-adapters.ts:213 — buildClaudeCommand() — complexity 27 (max 15)
2. src/term-commands/agents.ts:499 — launchTmuxSpawn() — complexity 22 (max 15)

These were introduced across recent PRs that used [skip ci] version bumps, masking the failures.

Fix needed

Refactor both functions to reduce cognitive complexity below 15. Extract helper functions for the branching logic.

Priority

P0 — blocks all npm @next publishes from dev.