fix(planning): remove unnecessary global flag from module-level regex

[lifrary]

Problem

TEAM_LAUNCH_RE and RALPH_LAUNCH_RE in src/planning/artifacts.ts are declared at module level with the /g (global) flag, but each regex is only used with a single exec() call per function invocation.

The /g flag causes RegExp objects to maintain internal lastIndex state between calls. The current code works around this with manual lastIndex = 0 resets before each exec(), but this pattern is fragile — if the regex is ever reused elsewhere without the reset, it will silently fail to match.

// Before: /g flag requires manual lastIndex reset
TEAM_LAUNCH_RE.lastIndex = 0;
const match = TEAM_LAUNCH_RE.exec(content);

Fix

• Remove /g flag from both TEAM_LAUNCH_RE and RALPH_LAUNCH_RE
• Remove the now-unnecessary lastIndex = 0 reset lines

// After: no /g flag, no lastIndex state to manage
const match = TEAM_LAUNCH_RE.exec(content);

Verification

• All 17 existing tests in src/planning/__tests__/artifacts.test.ts pass
• No other files reference these regex constants (confirmed via codebase grep)
• Behavioral change: none — exec() without /g returns the same first match