Refresh or retire ROADMAP.md before the next public release

[tpn]

Superseded by #53, which now includes removal of ROADMAP.md. The removal remains pending that PR's review and merge; no separate roadmap issue is needed.

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ROADMAP.md still describes plans after v0.1.0. Before the next public release, reconcile it with the implemented workflows and current release priorities, or retire it in favor of maintained GitHub issues.

The performance-baseline item also leaves the intended workloads, publication format, and ownership unspecified. PR #3 is being narrowed to benchmark instructions and interpretation; individual machine measurements remain review evidence. That documentation change does not establish a maintained release benchmark program.

Proposed resolution:

• Check each roadmap item against current code and release work. Remove completed or obsolete promises and link retained work to concrete issues.
• Keep a short roadmap only if a maintainer will own it. Otherwise remove the file and use the issue tracker for planned work, updating any references.
• If representative GPU baselines remain planned, define the workloads, hardware scope, reproducibility evidence, and where reports will be published in a separate tracked task. Do not make a new performance-reporting system a prerequisite for this release.
• Verify that the resulting public guidance describes the upcoming release accurately and makes no unsupported performance commitments.

This issue covers the roadmap decision and documentation, separately from the XRay changes in #2, #3, and #4.