fix(transport): isolate incompatible Telegram updates

[iriswolf]

Problem

A valid Telegram Bot API 10.2 rich-message update used ordered-list type "1", but the generated schema required the invalid literal "one". Long polling then classified the deterministic schema failure as transient and retried the same update forever, blocking all later updates.

Generator correction: IWFTech/TelegramSchemaGenerator#22.

Changes

• refresh the generated rich-list models without the invalid discriminator;
• decode getUpdates results one update at a time in the built-in transport path;
• stop retrying deterministic schema decode failures as transient request failures;
• add ITelegramUpdateDecodeFailurePolicy with fail-closed Stop and explicit Skip decisions;
• apply the same policy to syntactically valid webhook updates that do not match the installed schema;
• preserve malformed webhook payload handling as 400 and direct ITelegramClient.SendAsync(new GetUpdates()) as strict/atomic;
• log only update id, JSON path, and SHA-256 fingerprint, never the raw update payload;
• document acknowledgement, cancellation, quarantine, and idempotency semantics in English and Russian.

Touched hot paths

• TelegramUpdateBatchRequest and TelegramUpdateDecoder: per-element getUpdates decoding. Successful results use a readonly struct carrier; raw JSON and SHA-256 are created only on schema failure.
• TelegramLongPollingClient: ordered policy decision before offset advancement. Existing handler dispatch and successful-update acknowledgement order remain unchanged.
• TelegramRawWebhookEndpoint: parse envelope, identify update_id, then apply the shared decode policy. Normal handler execution remains unchanged.

Failure contract

Condition	Default result	Explicit Skip
Long-poll schema mismatch	throw once; do not advance offset	acknowledge only after policy completes
Webhook schema mismatch	HTTP 500	HTTP 200 only after policy completes
Policy throws or is cancelled	no acknowledgement	no acknowledgement
Malformed webhook JSON/envelope	HTTP 400	policy is not called

Verification

• Release build: 0 warnings, 0 errors
• Strict analyzers: passed
• Fast suite: 863 passed
• Package smoke: 4 passed
• Style and whitespace formatting: passed
• git diff --check: passed