chore(cleanup): remove dead lib/ duplicates + legacy OCaml prototype (#333)

## Housekeeping — remove provably-dead orphaned files

Follow-up to the Hypatia triage (#320). Two independent commits so you
can keep either alone.

### Commit 1 — dead `lib/` duplicates
`lib/linter.rs` + `lib/formatter.rs` are orphaned duplicates of the live
`src/ephapax-tools/src/{linter,formatter}.rs`. `lib/` has **no
`Cargo.toml`**, is **not a workspace member**, and **no manifest /
source / doc references it** — never built. Also retires the
`unwrap_dangerous_default` finding the triage had to exempt (its
`.hypatia-ignore` entry is dropped).

### Commit 2 — legacy OCaml prototype *(drop this commit if you want it
kept as an archive)*
`src/{lexer,parser,ast,typecheck}.ml` — a ~76KB early OCaml prototype
superseded by the Rust workspace. No `dune-project` / OCaml toolchain,
no references, last touched only by a cosmetic CI fix. Retires 4 `SD009`
(missing-SPDX) findings **without** an owner-gated licence edit — by
removal rather than header-stamping dead files.

**Evidence:** `lib/` absent from `Cargo.toml` members; `grep` finds no
`path="lib"`, no `mod`/`include!`/`include_str!`, and no `.adoc`/`.md`
links to any removed file.

> Verified dead, not just unused — but it's deletion of files I didn't
author, so it's a **draft** for your review. Also fixed locally (not in
this PR): the stale repo-local `user.signingkey` GPG override in
`.git/config` that was breaking SSH signing.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.hypatia-ignore

@@ -44,25 +44,6 @@ cicd_rules/banned_language_file:formal/Makefile.conf
 # handled by in-file `hypatia: allow` directives, not here.)
 code_safety/admitted:formal/Semantics.v
 
-# ─── Stale duplicate linter (lib/linter.rs) ────────────────────────────────────
-#
-# lib/linter.rs (178 lines) is a stale/legacy sibling of the live
-# src/ephapax-tools/src/linter.rs (920 lines). Its two `line.find(..).unwrap_or(0)+1`
-# sites compute 1-based diagnostic columns; 0 is a benign "column 1" default, not a
-# masked fault. Exempted pending an owner decision on whether to remove the duplicate.
-code_safety/unwrap_dangerous_default:lib/linter.rs
-
-# ─── SD009: legacy OCaml files without SPDX headers (src/*.ml) ──────────────────
-#
-# src/{lexer,parser,ast,typecheck}.ml are legacy OCaml artefacts in a Rust/Coq/Idris
-# project (the live type checker is Rust). Adding licence headers is an SPDX edit,
-# which estate policy reserves for the owner (no-automated-licence-edits). Flag-only:
-# exempted here and surfaced to the owner — these are also candidates for removal.
-structural_drift/SD009:src/lexer.ml
-structural_drift/SD009:src/parser.ml
-structural_drift/SD009:src/ast.ml
-structural_drift/SD009:src/typecheck.ml
-
 # ─── SD022: doc references to pre-restructure directories (deferred doc refresh) ─
 #
 # EXPLAINME/README/ROADMAP.adoc + tests/fuzz/FUZZING_GUIDE.md reference dirs