Update pilegram to latest

Bumps the pilegram flake input 17eb95c → 04318a3. Notable upstream
changes:

- Use the agent's home dir as the shared working directory
- Expose extension tools to the agent session
- Exit on a fatal poll-loop crash instead of going deaf
- Sanitize the finalized answer and the live draft; fall back to
  plain text when a finalized HTML chunk is rejected
- Various fixes: avoid double voice notes, bound the Writer 429 retry
  loop, validate --poll-timeout, release sessions on topic close
- Document the trust model and add tests

Pilegram's own nixpkgs pin is unchanged. Verified
packages.aarch64-linux.default builds via the linux-builder.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ngalaiko