feat(telemetry): fix escapes, add alerts, and add test utilities

[jbuckmccready]

Summary

• Fixed logfmt quoting and escaping for quotes, backslashes, equals signs, whitespace, and control characters.
• Refactored to use precomputed encoding plans to avoid excessive repeated calls to formatter functions to determine byte lengths and need for quoting.
• Added .alert(.dev | .operator) logging fields with configurable panic policies in tests (logged alert concept is described in this PR: test(gossip): pilot for component tests #1744)
• Introduced TestLogStore for capturing, iterating, inspecting, and resetting structured logs.

NOTE: no tests inspect logs in this PR since there isn't really a good use case currently in gossip, but it still asserts there is no logged alerts (using TestLogStore in the TestNode gossip harness). It would look something like this:

    var logs = test_node.logs().iterator();
    const record = logs.next() orelse return error.ExpectedLog;
    try std.testing.expectEqual(lib.telemetry.log.Level.err, record.level);
    try std.testing.expectEqualStrings("processMessage", record.scope);

    const propagated_record = logs.next() orelse return error.ExpectedLog;
    try std.testing.expectEqual(lib.telemetry.log.Level.err, propagated_record.level);
    try std.testing.expectEqualStrings("processPacket", propagated_record.scope);
    try std.testing.expectEqual(null, logs.next());

[Copilot]

Pull request overview

This PR enhances the telemetry logging system by fixing logfmt escaping/quoting, adding a first-class “alert” field for targeted operational signaling, and introducing test utilities to capture and assert on structured logs in in-process tests.

Changes:

• Added Alert support and .alert(.dev | .operator) logging fields, plus test-time panic policies for alert emission.
• Refactored log encoding to use precomputed encoding plans (byte lengths + quoting decisions) to avoid repeated formatter passes and improve correctness for escaping.
• Introduced TestLogStore and integrated it into the gossip TestNode harness to capture logs and enforce “no alerts emitted” behavior by default.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
v2/lib/telemetry/tests/TestLogStore.zig	New in-memory structured log capture utility for tests, with optional panic-on-alert behavior.
v2/lib/telemetry/tests.zig	Ensures TestLogStore tests are included in the telemetry test suite.
v2/lib/telemetry/log.zig	Adds Alert, introduces encoding plans, and implements logfmt quoting/escaping fixes with new tests.
v2/lib/telemetry.zig	Exposes TestLogStore, adds .alert() to the logger API, and uses encoding plans during logging.
v2/lib/gossip/tests/TestNode.zig	Integrates TestLogStore into the gossip test harness and routes node logs into it.

Comments suppressed due to low confidence (1)

v2/lib/telemetry/log.zig:1024

• LogfmtEscapingWriter.drain assumes data.len >= 1 and will underflow / OOB if invoked with an empty slice list. Add an assertion (or early return) to guard against that case.

        const self: *LogfmtEscapingWriter = @alignCast(@fieldParentPtr("writer", w));
        const rest = data[0 .. data.len - 1];
        const pattern = data[data.len - 1];

---

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[jbuckmccready]

Added assertions (it's required by the std Writer.drain contract to be non-zero): 7eddd95

[jbuckmccready]

Adjusted the comment for clarity: 9d827ca

[codecov]

Codecov Report

❌ Patch coverage is 97.74648% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
v2/lib/telemetry/tests/TestLogStore.zig	97.90%	4 Missing ⚠️
v2/lib/telemetry.zig	70.00%	3 Missing ⚠️
v2/components/gossip/tests/TestNode.zig	83.33%	1 Missing ⚠️

Files with missing lines	Coverage Δ
v2/lib/telemetry/log.zig	65.05% <100.00%> (ø)
v2/components/gossip/tests/TestNode.zig	94.87% <83.33%> (ø)
v2/lib/telemetry.zig	90.42% <70.00%> (ø)
v2/lib/telemetry/tests/TestLogStore.zig	97.90% <97.90%> (ø)

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[dnut]

Did you try this already and it had a problem?

Suggested change

	const AlertValue = struct {
	const value = @tagName(audience);
	};
	return self.field("alert", &AlertValue.value);
	return self.field("alert", @tagName(audience));

tagName already returns a pointer. You don't need a pointer to a pointer. I think you can eliminate this struct too since the lifetime of the pointer returned by tagName should be static.