Migrate selection-clear onto the record-mutation lifecycle driver

[HynLcc]

What

Migrate the selection-clear runner kind (1 case:
selection-clear/flat-1k-20fields-cell-clear-stream) onto the existing
record-mutation-lifecycle.ts driver, reusing it rather than building a new
one. It is the 4th member (after record-update / record-create / record-reorder).

selection-clear matches the family shape — single seeded table → one measured
bulk mutation (clear-stream) → post-op verify → restore-or-delete — but its
legacy artifact is [prepare, clear, verify] with no seedReady phase and a
separate verify phase. To fit without drifting the contract:

• driver: assertSeedReady is now optional. The three existing members
  all define it, so their code path and artifacts are byte-identical (proven by
  regression diff). selection-clear omits it → driver emits no seedReady phase.
• runner: runMeasuredOperation bundles the trace-wrapped, routing-asserted
  clear (primary metric clear1kMs) + the post-op full-scan verify into one
  primary measurement; a one-line buildResult adapter splits it back so
  buildSelectionClearResult and the [prepare, clear, verify] artifact are
  unchanged.
• seed mode stays bespoke: its artifact intentionally carries a seedReady
  phase (the inverse of execute), so routing both modes through one spec would
  push that asymmetry into the driver.

Verification (local, execute, v1+v2)

• pnpm check green.
• baseline A vs B: 8/8 pass, zero new diff masks needed.
• G1 baseline vs candidate: 8/8 pass — selection-clear plus
  record-update / record-create / record-reorder regression (shared driver
  touched).
• negative: perturbing phases[0].name, details.operation,
  fullScan.scannedRecords each fails the diff; a masked metric-value change
  still passes.
• candidate artifacts: result=pass, routeMatched=true, actualXTeableV2
  matches engine, fullScan.scannedRecords == rowCount (1000), clear1kMs
  (1359ms v1 / 765ms v2) far below max 90000.

Protected surface

No changes to cases/**, registry.ts, framework/types.ts config interfaces,
framework/artifacts.ts, scripts/diff-artifacts.mjs, or ../teable-ee. Tracker
updated to 18/35 runner kinds · 22/55 cases.

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