Add Opinion Wars: week-long two-faction battles attached to posts

A new post attachment type beside polls: the composer gains a Start
Opinion War builder (same disabled-inputs opt-in as the poll builder)
that names exactly two factions; the battle runs for exactly 7 days
from post creation. Members join a side, may defect at any time
(damage already dealt stays with the faction it was dealt to), and
fight once per 24 hours per battle. A fight spends 25 Code Farm coins
and deals deterministic level-weighted damage: 100 + 10 * min(level,
20) HP, so a newcomer deals 110 and a veteran caps at 300 - no
randomness anywhere.

The battle renders on the post card as a CSS pixel-art battlefield
(box-shadow sprites: castles, faction flags, marching soldiers, a
flickering campfire; steps() animation, disabled under reduced motion)
with live HP bars, a countdown, the viewer's faction strip, top
contributors and an event ticker. Live frames ride pub/sub on
public.battle.{uid} via a relay on the service-lock owner, with the
durable opinion_war_events trail (per-war atomic seq) as the source of
truth and a 15s incremental poller as fallback. /battles lists battles
with active/ended/mine filters, search and pagination.

Every mutation is a conditional UPDATE via conditional_update_row: the
fight sequence claims the cooldown first, then spends coins, then lands
the damage, compensating earlier steps on any later refusal so a crash
costs a turn, never coins. Resolution is lazy on read (no cron):
an exactly-once CAS computes the winner in the statement, awards XP
(participation, winner bonus, top damage dealer bonus; draws pay
participation only), emits the result event and notifies fighters. The
OpinionWarService backstop resolves unviewed wars and sends
fight-ready notifications, exactly-once via a marker CAS.

Fan-out: battle notification type, four badges, audit keys
(battle.create/join/switch/fight/resolve), Devii actions (join/fight
confirm-gated), API docs group, docs prose page, sitemap and topnav
entries, REPORTABLE_TARGETS registration, post-delete cascades,
README and nested CLAUDE.md documentation.

Verified with the four-layer procedure: property checks over the full
damage domain, 1200-step stateful fuzz (hp-sum invariant, coins never
negative, resolved totals frozen), and real 8-process races proving
exactly-once semantics for concurrent fights, double-spends across two
wars, resolution XP and double-joins. Persisted tests in
tests/unit/services/opinionwar, tests/api/battles, tests/e2e/battles
and tests/api/posts/create.py.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CLAUDE.md

@@ -155,6 +155,7 @@ Nested `CLAUDE.md` files (loaded automatically by Claude Code only when a file i
 | `devplacepy/services/pubsub/CLAUDE.md` | Database-free pub/sub bus |
 | `devplacepy/push/CLAUDE.md` | Push notification providers: the `PushProvider` protocol, the registry, Web Push and APNs, registration storage |
 | `devplacepy/services/game/CLAUDE.md` | Code Farm idle game (economy invariants, raids, the one-pure-function rule) |
+| `devplacepy/services/opinionwar/CLAUDE.md` | Opinion Wars (week-long faction battles on posts: atomic fight/resolve transitions, cooldown-before-coins compensation, event seq allocation, relay-on-lock-owner) |
 | `devplacepy/services/quiz/CLAUDE.md` | Quizzes (the terminal publish lock, attempt atomicity, answer-key withholding, AI free-text grading, the best-attempt scoreboard) |
 | `devplacepy/services/CLAUDE.md` | Background task queue, AI correction/modifier, presence, live view relay, `BaseService`/`ServiceManager` |
 | `devplacepy/database/CLAUDE.md` | Dataset rules, indexing conventions, soft delete, tables, site settings |
@@ -201,6 +202,7 @@ Routers in `devplacepy/routers/` are organised as a **directory tree that mirror
 | `/game` | game/ package - see `services/game/CLAUDE.md` |
 | `/reports`, `/admin/moderation`, `/workspaces` | reports.py, admin/moderation.py, workspaces.py - see `services/moderation/CLAUDE.md` |
 | `/quizzes` | quizzes/ package - see `services/quiz/CLAUDE.md` |
+| `/battles` | battles.py - see `services/opinionwar/CLAUDE.md` |
 | (none) | push.py (web push/PWA), docs.py (see `routers/docs/CLAUDE.md`) |
 | `/pubsub` | pubsub.py - see `services/pubsub/CLAUDE.md` |
 | (none) | seo.py - `/robots.txt`, `/sitemap.xml` |