fix: handle Telegram channel-post commands

[lucientavano]

Bug Description

Telegram channel posts containing slash commands were not reaching the command handler, so commands like /sethome failed when posted from channels.

Root Cause

The Telegram adapter only registered the normal command handler, and _handle_command() only read update.message. Telegram channel-post commands arrive via update.channel_post / update.edited_channel_post, so they were ignored.

Fix

• register a Telegram command handler for filters.UpdateType.CHANNEL_POSTS & filters.COMMAND
• normalize command updates through a small helper that accepts message, edited_message, channel_post, and edited_channel_post
• add regression tests covering both channel-post command routing and handler registration

How to Verify

1. source venv/bin/activate && python -m pytest tests/gateway/test_telegram_channel_posts.py tests/gateway/test_telegram_group_gating.py tests/gateway/test_telegram_reactions.py -q
2. Post a slash command like /sethome in a Telegram channel where Hermes is admin
3. Confirm the command reaches the gateway command handler instead of being ignored

Test Plan

• Added regression test for this bug
• Existing targeted Telegram tests still pass
• Manual verification in a live Telegram channel

Risk Assessment

Low — the change is narrowly scoped to Telegram command update routing and is covered by targeted regression tests.

[lucientavano]

Operator note: I ran a broader python -m pytest tests/gateway/ -q sweep after landing this fix. The gateway suite is currently not green on upstream main; I reproduced representative failures on clean HEAD without this branch checked in. The failures appear pre-existing and unrelated to this PR (display_config imports, matrix sync auth retry tests, Telegram approval-button tests, session hygiene/env tests, and Feishu test drift). This PR stays intentionally scoped to Telegram channel-post command routing.

[alt-glitch]

Related to #3634 (open issue for same bug) and closed #3683 (prior PR attempt). This PR appears to be a fresh fix for the same root cause: Telegram adapter ignoring channel_post updates.

[teknium1]

Thanks for the focused Telegram regression fix. This is now superseded by a broader implementation already on main.

• Automated hermes-sweeper review verified plugins/platforms/telegram/adapter.py:7468-7476 resolves channel posts through Update.effective_message, and :7511-7531 routes the resulting message through the COMMAND event path.
• tests/gateway/test_telegram_channel_posts.py:168-181 covers command dispatch from a channel post, including channel identity.
• Commit 704872a62f87c642a0c69fcb0f138d48896e0d59 (fix(telegram): handle channel post updates) shipped in v2026.5.28. The related fix(telegram): handle channel post updates #25327 discussion also records that this broader effective-message approach superseded the same Telegram adapter does not process channel_post updates #3634 root cause.

Closing as implemented on main.