Triage and resolve lingering source-code TODO comments

[nohwnd]

Context

A test-suite audit (see #2764) surfaced ~58 TODO comments scattered across src/. None are production blockers — the test suite is green and behavior is correct. These are accumulated design-debt notes worth tracking in one place so the information isn't lost in comments. This is housekeeping, not a bug.

Grouped by theme below. Each line is a file:line reference (line numbers approximate; they drift as code changes).

P1 — Latent dead code (cheap wins)

• src/functions/TestResults.NUnit25.ps1:320,334 — the reason/message block for Skipped/Inconclusive is unreachable: it guards on $TestResult.FailureMessage, which is never populated for those states (verified — empty at the source, so the emitted NUnit2.5 XML is still valid but the block is dead). :334 also guards on FailureMessage but writes DisplayErrorMessage. Remove or wire up correctly.
• src/Pester.Runtime.ps1:1069 — commented-out Write-Host debug line tagged #TODO; just delete.

P2 — Dead-code "Remove?" decisions

• src/Pester.Utility.ps1:314,420
• src/functions/Coverage.ps1:154,170,182 — hashtable/IDictionary config syntax: implement or remove.
• src/functions/Mock.ps1:1841,1861

P3 — Unify error formatting across NUnit/JUnit writers

Several writers format errors locally instead of via one shared core function (so screen vs. report can diverge).

• src/functions/TestResults.NUnit25.ps1:272,348,349,363
• src/functions/TestResults.NUnit3.ps1:594,595,614

P4 — Mock internals / "resolve path safely"

• src/functions/Mock.ps1:1181,1186 — $______isInMockParameterFilter hack + bound-parameter binding note.
• src/functions/Pester.SessionState.Mock.ps1:35,40,45 — resolve path safely (×3).
• src/functions/Pester.SessionState.Mock.ps1:464,557,892

P5 — Runtime concepts to clarify ("before shipping")

• src/Pester.Runtime.ps1:180,2605 — Id used by NUnit2.5/3 grouping; find a better mechanism.
• src/Pester.Runtime.ps1:1961,1982,2300,2324,2581
• src/Pester.RSpec.ps1:309,310,314 — error-writing logic coupled to a plugin; separation of concerns.

P6 — Coverage breakpoint-merge implementation

• src/functions/Coverage.ps1:588,595 — quick merge of breakpoint lists; avoid splitting/merging twice.
• src/functions/Coverage.Plugin.ps1:124 — check config for coverage mode instead of inferring.

P7 — Should-BeEquivalent verbose-output polish

• src/functions/assert/Equivalence/Should-BeEquivalent.ps1:78,231,244,266,332,592,607,705

P8 — SkipRemainingOnFailure: expose data via $Context

• src/functions/Get-SkipRemainingOnFailurePlugin.ps1:57,132 — use $Context.GlobalPluginData.SkipRemainingOnFailure.* once exposed.

P9 — Low-priority informational notes (likely leave as-is)

• src/Format.ps1:170 · src/Main.ps1:465,584,585 · src/Pester.Utility.ps1:449 · src/functions/Describe.ps1:195 · src/functions/Output.ps1:426 · src/functions/TestDrive.ps1:190 · src/functions/TestRegistry.ps1:110

---

No action is required for production quality; resolve opportunistically. The P1 items are the only quick "real" cleanups.