## Summary
Adds a second generation of run-ops id, plus the resolver that reads a
store key straight out of an id. A gen-2 id keeps the existing
26-character layout, but the character at index 24 becomes a routing
shard key instead of a region code, and the version character at index
25 becomes `"2"`. Nothing mints gen-2 ids yet, so this is inert on
merge.
## Design
The version character is a single character, so the gen-1 and gen-2
shape checks can never both match. That is what makes the two
generations provably disjoint rather than disjoint by convention.
```ts
resolveShard(id) // gen-2 body -> its shard key, [a-z0-9]
// gen-1 v1 body -> "new"
// anything else -> "legacy"
```
`resolveShard` is total: it returns a key for any input string,
including an empty or malformed one, and never throws.
`classifyResidency` keeps its signature and its two values, and now
reports gen-2 ids as part of the dedicated family, so existing consumers
of that boolean are unaffected.
The body stays 26 characters rather than 27 deliberately. The older
27-character format is still in the wild and has to keep resolving to
legacy, and a longer gen-2 shape would need probabilistic disambiguation
against it. A rare misroute is not an acceptable property for a routing
key.
The one behavior change is that a 26-character body ending in `"2"` now
routes by its shard key instead of falling back to legacy. Two test
assertions pinned the old result and are updated here. A repository-wide
search confirms they are the only two of their kind.
Verified against the full run-store corpus (68 files, 370 tests) with no
test-file changes there, plus the run-engine residency and waitpoint
suites. No changeset: the new surface has no caller, so a version bump
would tell a user nothing.
Daniel Sutton
c5c2ea92ca