Improvements to the trace analysis feature

[polpielladev]

While using the trace analysis feature of the skill, I came across two different things:

• Signpost analysis was always returning empty
• We did not handle multi-run traces

[AvdLee]

LGTM but let's also see what Copilot has to say

[Copilot]

Pull request overview

This PR improves the Instruments trace analysis scripts used by the SwiftUI expert skill by fixing signpost parsing (previously yielding empty results) and adding proper support for multi-run .trace files.

Changes:

• Added a safe helper for selecting the first present XML column to avoid Element truthiness pitfalls that were dropping valid timestamps.
• Introduced per-run TOC metadata (RunInfo) and added --run / --list-runs support, threading run= through all lane analyzers and discovery commands.
• Expanded signpost discovery to read both os-signpost-interval (pre-paired intervals) and os-signpost (raw events) while avoiding duplicates.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
swiftui-expert-skill/scripts/instruments_parser/xml_utils.py	Adds first_present() to correctly choose between alternative timestamp keys.
swiftui-expert-skill/scripts/instruments_parser/xctrace.py	Refactors TOC parsing to be run-aware and exports schemas by run via XPath.
swiftui-expert-skill/scripts/instruments_parser/time_profiler.py	Plumbs run through to schema export.
swiftui-expert-skill/scripts/instruments_parser/swiftui.py	Plumbs run through to schema export for SwiftUI lane schemas.
swiftui-expert-skill/scripts/instruments_parser/hitches.py	Plumbs run through to schema export.
swiftui-expert-skill/scripts/instruments_parser/hangs.py	Plumbs run through to schema export.
swiftui-expert-skill/scripts/instruments_parser/events.py	Fixes signpost discovery: reads os-signpost-interval + os-signpost, pairs events, and avoids duplicates.
swiftui-expert-skill/scripts/instruments_parser/causes.py	Uses first_present() and plumbs run through to schema export.
swiftui-expert-skill/scripts/analyze_trace.py	Adds --run / --list-runs support and routes analysis/discovery to the selected run.
swiftui-expert-skill/references/trace-analysis.md	Documents multi-run usage and the new CLI flags.