feat(signal): add read receipt support

[gibbsoft]

Summary

• Send read receipts after handling inbound Signal messages
• Controlled by SIGNAL_SEND_READ_RECEIPTS env var (defaults to true) or send_read_receipts in signal platform config

Motivation

Signal shows messages as unread/undelivered when the recipient doesn't send read receipts. This makes hermes-agent behave like a proper Signal client.

Test plan

• Send a message to hermes via Signal — verify blue double-tick (read) appears on sender's device
• Set SIGNAL_SEND_READ_RECEIPTS=false — verify no read receipts are sent

[Copilot]

Pull request overview

Adds optional outbound Signal read receipts so Hermes behaves more like a native Signal client, controlled via configuration/env.

Changes:

• Add send_read_receipts option to Signal adapter and send a read receipt after processing inbound messages.
• Add SIGNAL_SEND_READ_RECEIPTS env override (defaulting to true) into Signal platform extra config.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
gateway/platforms/signal.py	Adds adapter config flag and implements sendReceipt call after handling inbound messages.
gateway/config.py	Adds env override plumbing for SIGNAL_SEND_READ_RECEIPTS into the Signal platform config.

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[Copilot]

Env override adds SIGNAL_SEND_READ_RECEIPTS, but there’s no test asserting the default (true) or the false case in tests/gateway/test_signal.py::TestSignalConfigLoading.test_apply_env_overrides_signal. Please add assertions to prevent regressions (e.g., default enabled when unset, disabled when set to "false").

Suggested change

	"send_read_receipts": os.getenv("SIGNAL_SEND_READ_RECEIPTS", "true").lower() in ("true", "1", "yes"),
	"send_read_receipts": _coerce_bool(os.getenv("SIGNAL_SEND_READ_RECEIPTS"), default=True),

[Copilot]

send_read_receipts defaults to False here, but the PR description (and the env override in gateway/config.py) indicate the default should be True. As written, read receipts will be disabled by default when Signal is configured via file config (no env override), which is inconsistent with the intended behavior. Consider changing the fallback default to True (or otherwise make the default consistent across env + config).

[Copilot]

This will also send a read receipt for "Note to Self" messages (is_note_to_self=True) where sender is the adapter's own account (self-message filtering is explicitly bypassed for that case). Sending read receipts to the local account is unnecessary and may cause unexpected RPC errors/noise. Consider adding a guard (e.g., skip when is_note_to_self or when sender == self._account_normalized).

Suggested change

	# Send read receipt if enabled
	if self.send_read_receipts and sender and ts_ms:
	# Send read receipt if enabled (but skip self / note-to-self messages)
	if (
	self.send_read_receipts
	and sender
	and ts_ms
	and not is_note_to_self
	and sender != getattr(self, "_account_normalized", None)
	):

[Copilot]

New behavior (sending read receipts after handling inbound messages) isn’t covered by the existing Signal adapter test suite (tests/gateway/test_signal.py). Please add tests that verify _rpc("sendReceipt", ...) is called when send_read_receipts is enabled, and not called when disabled (and for Note-to-Self if that’s intentionally excluded).