First slice of #64176's observer-hook half — a normalized-envelope inbound
event hook, replacing raw-SDK handler args with a stable contract (per #64176's
"normalized versioned envelopes only; raw SDK gated behind a capability" rule).
- VALID_HOOKS: register the four gateway_* names from #64176
(gateway_platform_event fires today; gateway_session_titled /
gateway_message_delivered / gateway_thread_created reserved pending #64176's
fire-sites).
- BasePlatformAdapter._fire_gateway_hook: reusable, has_hook-guarded,
per-call-isolated fire helper (the no-subscriber common case short-circuits).
- TelegramAdapter: a group-99 catch-all TypeHandler normalizes inbound updates
into gateway_platform_event envelopes. message_reaction -> {platform,
event_type:"reaction", payload{emojis, custom_emoji_ids, chat_id, message_id,
thread_id}} (custom-emoji reactions captured via custom_emoji_id; standard via
.emoji — no None in consumer-facing lists). Other update types return None
pending #64176's taxonomy (#64231). Normalization is wrapped so a malformed
update can't raise into PTB dispatch.
Observer-only — zero behavioral change to core dispatch. Supersedes the raw
inbound half of #62584 (telegram:update -> normalized gateway_platform_event).
Tests: VALID_HOOKS registration; _fire_gateway_hook routing/has_hook/isolation;
_normalize for standard, custom-emoji, and mixed reactions + non-reaction;
_on_platform_update firing + normalize-error isolation.
Ran code-review (high) + simplify before pushing.
Paolo Antinori
929be4d1aa