GoMud Playtest Harness v0.1.2

Adds admin web pages for the playtest module. Runtime behavior is otherwise
unchanged from v0.1.1.

What's new

Admin web pages (Modules → Playtest in the admin UI), per the maintainer's
v0.1.1 review suggestion:
- /admin/playtest-config — edit the module's keys (Enabled, SafeMode,
  SandboxZoneTag, DeathProtection, Beacons) in the web UI instead of
  hand-editing the overlay file. Changes apply on the next server restart.
- /admin/playtest-about — what the module does, its configuration, and
  room-tag usage.
Docs: an agent-side quickstart ("run your first playtest with Claude Code"),
and the goals file is now a first-class input in the driver
(/playtest <target> <personality> <goals> = where / role / what-to-test).

go run . module install playtest        # then:
go generate ./... && go build -o go-mud-server

Requirements unchanged: a GoMud with the AI port (in master) + the bundled
gmcp module for beacons.

playtest.tar.gz sha256:
8b9502da19221ff8365bd86c6efc0f90547ba8bd08f8a19a4ad3d3d13141ee12