feat(plan): render observed execution timing

[gbin]

Summary

• Add cu29-plan --logstats input with mission and graph-signature validation.
• Render packed proportional execution traces alongside the generated schedule.
• Show stage estimates, residual timing, carried-forward exclusions, and resource-overlap risk.
• Select the recorded mission when no explicit plan mission is requested.

Stack

PR 3 of 4.

• Depends on feat(logstats): export observed schedule timing #1250, which depends on fix(logstats): resolve config features and mission defaults #1249.
• The plan-log workflow PR feat(dx): add plan-log workflows #1245 is based on this branch.

Verification

• Rust formatting check passed for all changed Rust files.
• Diff whitespace check passed.
• Full workspace verification is deferred to CI because the local checkout is missing the optional sibling cu-vitfly path dependency.