Docs: Chez-only, drop the Janet-era references and obsolete migration notes

Bring the docs in line with the actual implementation now that Chez is the sole
substrate.

Deleted the migration/spike/handoff artifacts that only documented the Janet
era or the port effort: the port plan, phase-0 and foundational-runtime spike
writeups (+ the stray root-level copy), the self-hosting design notes, the
architecture-refactor plan, and spike/chez/RESULTS.md.

Rewrote the current reference docs against the Chez facts: building-and-deps and
tools-deps (no jpm/build step — bin/joltc off the checked-in seed, deps via
jolt.deps into ~/.jolt/gitlibs), libraries (SQLite is built-in jdbc.core over
libsqlite3, not a Janet driver), the conformance/spec test-flow docs (the Chez
corpus runner + certify, no .janet harnesses), and the transient / type-hint /
seed-overlay design notes (Chez representations: mutable transients, flat
copy-on-write vectors, HAMT maps, the seed/overlay twin). Fixed the README
collections line (vectors aren't 32-way tries) and added the ffi/transient gate
targets. rfc 0001's numerics open-question is resolved (the Scheme tower).

Renamed the built-in HTTP adapter to jolt.http.server only (dropped the
ring-janet.adapter alias — a Janet-era name).

test/chez/README.md

@@ -1,6 +1,6 @@
 # Chez test harness
 
-The correctness gate for jolt. Pure Chez (+ Clojure for the JVM oracle), no Janet.
+The correctness gate for jolt. Pure Chez (+ Clojure for the JVM oracle).
 Correctness is judged against the JVM-sourced conformance spec; the spec itself
 lives in `test/conformance/` (see its `SPEC.md`). Run the whole gate with `make
 test` from the repo root.

test/conformance/README.md

@@ -7,13 +7,14 @@
 
 The corpus (`test/chez/corpus.edn`) is jolt's host-neutral behavioral suite — one
 row per case: `{:suite :label :expected :actual}`, where `:actual` is a Clojure
-source expression and `:expected` its result (or `:throws`). Runtime harnesses
-(`test/chez/run-corpus-prelude.janet`, `run-corpus-zero-janet.janet`) replay it on
-each host and compare by value-equality.
+source expression and `:expected` its result (or `:throws`). The runtime harness
+(`host/chez/run-corpus.ss`, invoked by `make corpus`) replays it on Chez and
+compares by value-equality.
 
-Historically every `:expected` was **hand-written by jolt developers**. That makes
-the corpus a fine regression suite but a weak *specification*: it certifies jolt
-against its authors' beliefs, not against Clojure. This directory closes that gap.
+Every `:expected` is sourced from reference JVM Clojure, so the corpus is both a
+regression suite and a *specification* certified against Clojure rather than
+against its authors' beliefs. This directory holds the certification tooling that
+closes that gap.
 
 ## What's here
 
@@ -34,17 +35,17 @@ against its authors' beliefs, not against Clojure. This directory closes that ga
   entries with a tracked bead. These categories become the `:features` flags in
   conformance inc3.
 
-- **`certify-test.janet`** — gate wrapper. Skips cleanly when `clojure` (JVM) is
-  not installed; otherwise runs `certify.clj` and fails the build on a **NEW**
-  (unclassified) divergence or a **stale** allowlist entry. Flaky entries (JVM
-  result is timing-dependent, e.g. `future-cancel`) are tolerated either way.
+`make certify` is the gate wrapper. It skips cleanly when `clojure` (JVM) is not
+installed; otherwise it runs `certify.clj` and fails the build on a **NEW**
+(unclassified) divergence or a **stale** allowlist entry. Flaky entries (JVM
+result is timing-dependent, e.g. `future-cancel`) are tolerated either way.
 
 ## Running
 
 ```sh
-clojure -M test/conformance/certify.clj                      # gate (exit≠0 on new/stale)
+make certify                                                 # the gate wrapper (skips if clojure absent)
+clojure -M test/conformance/certify.clj                      # gate directly (exit≠0 on new/stale)
 clojure -M test/conformance/certify.clj test/chez/corpus.edn --edn /tmp/report.edn  # full machine-readable report
-janet test/conformance/certify-test.janet                    # the gate wrapper
 ```
 
 ## Current state

test/conformance/SPEC.md

@@ -70,7 +70,6 @@ implements. Current profile (≈2670 portable, ≈249 non-portable):
 | `:concurrency/snapshot` | isolated-heap futures/agents/pmap — captured atoms are snapshotted, not shared |
 | `:host/jvm-interop` | Java classes / `instance?` on host classes / proxy / bean / definterface |
 | `:host/arrays` | Java arrays (`into-array`, `int-array`, …) |
-| `:host/janet` | Janet host interop (`janet.*`) |
 | `:async/core-async` | `clojure.core.async` channels/`go` |
 | `:runtime/eval` | runtime `eval` / `load-string` |
 | `:reader/jolt` | jolt reader features (`#?(:jolt …)`) + syntax-quote literal collapse |