docs: cut 1.3.3 notes for the tier work

CHANGELOG gets all five breaking changes, not the one the draft had:
ThinkingCapability's constructor, two ports that grew a parameter with
no default, resolve_thinking's new return type, and ProviderProfile's
single wire field. Behaviour changes get their own section, including
the one that is easy to miss — the openai fallback segment no longer
refuses an unknown shape, so a downstream that parks a foreign model
there and asks for thinking used to fail at assembly and now sends
nothing at all. minimax is called out as the exception it is: the gateway
proved M3 does not think without a parameter, so that segment keeps its
medium and its downstreams see no change this release.

The capability table is reported as it stands — 17 of 24 rows measured,
7 still on documentation, with the reason each one went unmeasured, so
nobody reads "measured" into a row that is a guess. The auto limitation
and its deliberate MiniMax-M3 inconsistency are written down rather than
left for someone to trip over; issue #21 holds the real fix.

ARCHITECTURE had five claims that measurement showed had gone false:
the cache key formula, the field count, the reconcile predicate and its
throttle key, and two field lists. README's FIELD set was missing the
two new keys it calls exhaustive.

docs-convention still opened by announcing a 17-page site that has not
existed since August. It now says what is actually there — one placeholder
page pointing at .env.example, CHANGELOG and the source docstrings — and
says which four files carry the sync gate while the site is down.

src/polygateway/__init__.py

@@ -50,7 +50,7 @@ from polygateway.types import (
     ThinkingObservation,
 )
 
-__version__ = "1.3.2"
+__version__ = "1.3.3"
 
 __all__ = [
     "DEFAULT_PROFILES",