Plan v1.10 Quality of Life

Ten tasks across four features, each ending in an independently testable
deliverable. Written against the approved spec.

The self-review pass found and fixed four things:

- Two steps told the implementer to look a value up rather than giving it.
  Replaced with the real ones: migrateGain = floor(sqrt(lifetimeRun / 1e6) *
  mult), so 1e8 grants exactly 10 cores, and meta.shardUpgrades is the shard
  levels property.
- The spec asks for an "exactly on a threshold" boundary case that no task
  covered - sitting on 25 must target 50, not re-buy 25.
- The spec requires finish to report a new best only when the score actually
  beat the prior one; that behaviour was implemented but untested.
- Passing ctx into the badge case was a step with no code, and the obvious
  shortcut - hand-rolling a partial ctx - would satisfy every achievement that
  exists today and break silently on the next one added.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: Evan Phyillaier