fix: guard float(os.getenv) against ValueError in gateway platform adapters

[vominh1919]

Problem

Several gateway platform adapters cast environment variables directly via float(os.getenv(...)) without try/except. If any env var is set to a non-numeric string (e.g., HERMES_TELEGRAM_TEXT_BATCH_DELAY_SECONDS=abc), the platform adapter crashes with ValueError during __init__, preventing the entire gateway from starting.

Affected files and variables:

• telegram.py: MEDIA_BATCH_DELAY_SECONDS, TEXT_BATCH_DELAY_SECONDS, TEXT_BATCH_SPLIT_DELAY_SECONDS (3 instances)
• discord.py: TEXT_BATCH_DELAY_SECONDS, TEXT_BATCH_SPLIT_DELAY_SECONDS (2 instances)
• wecom.py: TEXT_BATCH_DELAY_SECONDS, TEXT_BATCH_SPLIT_DELAY_SECONDS (2 instances)

Note: telegram.py already has a _env_float() helper (line 776) with proper try/except handling, but it was not used in __init__.

Fix

Each float(os.getenv(...)) call is wrapped in try/except (ValueError, TypeError) with the original default value as fallback.

Diff: +28 lines, -7 lines across 3 files

Before vs After

Scenario	Before	After
Valid env var	Works	Works (identical)
Env var set to "abc"	ValueError crash → gateway won't start	Falls back to default value
Env var set to None string	TypeError crash	Falls back to default value

Impact

• Severity: MEDIUM — gateway startup crash from misconfigured env var
• Scope: Telegram, Discord, WeCom platform adapters
• Risk: Minimal — only adds error handling, no behavioral change on valid input

[alt-glitch]

Likely duplicate of #17905 (merged) — same root cause: unguarded float() env var casts in gateway platform adapters. #17905 already addressed this.

[alt-glitch]

Likely duplicate of #17905 (merged) — same root cause: unguarded float() env var casts in gateway platform adapters.

[teknium1]

Thanks for the defensive gateway hardening. This is already implemented on current main, so this PR is redundant.

• utils.py:421 defines env_float(), which falls back on malformed values instead of propagating ValueError / TypeError.
• The live Discord and WeCom adapters use it for the reported batch-delay settings at plugins/platforms/discord/adapter.py:829 and plugins/platforms/wecom/adapter.py:190.
• Telegram uses env_float() for media batching (plugins/platforms/telegram/adapter.py:546) and the stricter _env_float_clamped() path for text batching (plugins/platforms/telegram/adapter.py:558), which also rejects non-finite values.
• Commit a7dd98c8609c0d944e3c5dd0c5b9ee31dd99eb29 implemented the broader malformed numeric-env guard; the legacy gateway/platforms/{telegram,discord,wecom}.py paths in this diff were subsequently migrated to bundled platform plugins by 5600105478ffde29d7566b45421b100eaa29c4ef.

The earlier discussion linked #17905; current adapter coverage is independently present in the later broader safeguard above. Automated hermes-sweeper review.