Tracking: Missing exercises from problem specifications

Directly from `configlet info` (updated 2026-09-13).

There are 25 non-deprecated exercises in `exercism/problem-specifications` that are both unimplemented and not in the track config `exercises.foregone` array:

With canonical data:

- [ ] camicia
- [ ] complex-numbers
- [ ] custom-set
- [ ] dominoes
- [ ] dot-dsl
- [ ] forth
- [ ] go-counting
- [ ] grep
- [ ] ledger
- [ ] piecing-it-together
- [ ] pov
- [ ] pythagorean-triplet
- [ ] rational-numbers
- [ ] react
- [ ] rectangles
- [ ] relative-distance
- [ ] rest-api
- [ ] satellite
- [ ] sgf-parsing
- [ ] simple-linked-list
- [ ] tree-building
- [ ] zipper

Without canonical data:

- [ ] error-handling
- [ ] lens-person
- [ ] paasio