docs(pkg): canonical Nix-retirement inventory worklist (Wave 0) (#104)

Closes the actionable of #103 (Wave 0 of campaign #102; policy #101).

Read-only discovery over all **379** hyperpolymath repos (top-level
`HEAD`), committed as the durable worklist
`rhodium-standard-repositories/spec/nix-retirement-inventory.adoc`:

| Class | Count |
|---|---|
| Candidate (→ 14 waves) | 277 |
| Monorepo → handle at source | 8 |
| Excluded (standards, echidna #73) | 2 |
| Out-of-scope (no flake / no Guix) | 92 |

Verdicts are **provisional** — final keep/remove is per-repo at wave
time (`flake` inputs vs `Guix ∪ sealed-container`). The
`.guix-channel`-only and flake-without-Guix traps were checked and are
**empty**; the earlier triage's "my-lang = channel-only" was inaccurate
(my-lang has no flake.nix → out-of-scope). The `Wave` column is
authoritative for slicing the wave sub-issues.

Gate rules are **not duplicated** here — the artifact links to #102 /
`LANGUAGE-POLICY.adoc`.

Refs #103
Refs #101

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath