fix(ton-bridge): add fallback for missing customMessage in ton_bridge_custom_message

[konard]

Problem

ton_bridge_custom_message has customMessage listed as required in its JSON Schema parameters, but LLMs can and do call tools without providing required fields. When customMessage is omitted, params.customMessage is undefined, which gets passed directly to sdk.telegram.sendMessage(chatId, undefined, ...) — causing a crash.

Fix

Add a ?? fallback chain (per CONTRIBUTING.md guidelines — use ?? not ||) in the execute function:

const customMessage =
  params.customMessage ??
  sdk.pluginConfig?.customMessage ??
  "TON Bridge — The #1 Bridge in the TON Catalog\n\nClick the button below to open TON Bridge Mini App.";

This is consistent with how ton_bridge_open already handles params.message.

The fallback priority is:

1. LLM-provided params.customMessage
2. Operator-configured sdk.pluginConfig.customMessage
3. Hardcoded default message

Tests

Added 2 new unit tests:

• Falls back to sdk.pluginConfig.customMessage when param is missing
• Falls back to hardcoded default when both param and config are missing

All 27 tests pass.

Closes #31

[konard]

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[konard]

✅ Ready to merge

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