docs(bigshot.lic): v5.16.0 add YARD documentation throughout

Full YARD pass: 296 of 296 methods now carry @param/@return (plus
@raise/@note/@see/@yieldparam where relevant), and DebugLogger, Event,
BSAreaRooms, and Group each get a class-level doc explaining their
role. No behavior change - pure documentation.

Written from reading each method body, not generated from signatures,
so several carry information the code doesn't state on its face:

  - Group#member_online documents why nearly every Group method funnels
    through it: a follower whose Lich has exited raises
    DRb::DRbConnError on access, and the group has to survive that
    rather than letting it propagate into the leader's hunting loop.
  - Bigshot#ping's doc records that its `true` return value is
    irrelevant - the point is that a dead follower raises on the call
    itself, which is what actually gets it dropped.
  - add_event notes that :ATTACK is dropped once a follower's event
    stack backs up, so a lagging follower doesn't accumulate stale
    attack orders.
  - BSAreaRooms#build flags that it exits the script past 200 rooms,
    on the assumption the boundaries are misconfigured rather than the
    area genuinely being that large.
  - check_state_condition and initialize_command_data cross-reference
    each other via @note: a new command-check modifier added to one
    and not the other silently never parses.

Two mistakes caught and fixed during this pass, both confirmed to
predate this commit (i.e. present in the file this PR is based on, not
introduced by it): a duplicated description line on
BigshotCreature#gameobj, and an identical duplication on
still_targetable?, both artifacts of appending a short YARD summary
above a method that already had a full prose comment without checking
for one first. Fixed in place; a full-file scan confirmed no other
instances of the pattern.

Author: claude