Replay parallel worker debug output interleaved with tests

[nohwnd]

Fix #2825

Problem

When running with Run.Parallel = $true and Output.Verbosity = 'Diagnostic' (or Debug.WriteDebugMessages otherwise enabled), diagnostic output such as Mock debug messages was printed before the test results and detached from the test that produced it, so it was impossible to associate the output with a specific test.

Why it happened

In a parallel run each file executes in its own worker runspace. The worker runs silently (Output.Verbosity = 'None') and records the plugin events onto a tape that the parent replays in test order to produce console output. Debug output, however, went through Write-PesterHostMessage and was written straight to the host as the worker executed — it was never part of the replayed tape. So every worker's debug lines surfaced up front, out of order relative to the per-test output.

Fix

Capture the worker's host/debug output into the same event tape the recorder already uses, and replay it from the parent in tape order. Because each worker runs a single file synchronously, append order is already the correct order, so the debug lines come back interleaved with the per-test output they belong to instead of dumped up front.

• Output.ps1 — when a worker's parallelOutputTape is set, Write-PesterHostMessage appends the message to the tape (a Step = $null entry carrying the bound parameters) instead of writing to the host live.
• Pester.Parallel.ps1 — point the tape at the recorder's list so plugin steps and host/debug output share one ordered tape, and split the tape positionally at ContainerDiscoveryEnd so each host entry stays in the phase (discovery vs. run) it was produced in.
• Main.ps1 — the parent replays host entries (Step = $null) to the real host in position; the earlier warning about uncorrelated debug output is removed since the output is now correlated.

Tests

Replaced the two tests in tst/Pester.RSpec.Parallel.ts.ps1: one runs two files in parallel with Diagnostic output and asserts the debug output is captured and replayed interleaved with each file's tests (on PS7+ it also checks the second file's discovery output lands after the first file's result); the other asserts the run no longer warns about uncorrelated debug output. The full parallel suite (21 tests) and Output.Tests.ps1 (55 tests) pass, and the custom build analyzer reports no new findings in the changed files.