join deva launch receipts: goal attribution on sessions

[lroolle]

Description

deva --goal (thevibeworks/deva#499) writes launch receipts to
$XDG_DATA_HOME/ccx/launches/*.jsonl. ccx should join receipt->session
so sessions carry the goal they were launched under.

Details

• internal/launches: load receipts, index by cwd
• rule: a receipt stamps sessions in the same cwd starting within
  [ts-5m, ts+24h]; latest qualifying receipt wins
• ccx sessions: goal field in --json output, --goal SLUG filter
• receipts are advisory: missing dir/malformed lines never error
• session files stay untouched (read-only invariant)

Test Plan

• unit: match, latest-wins, 24h expiry, 5m grace, wrong cwd, bad lines
• live: receipt stamped by deva --goal annotates a real session