feat: give the public surface an HTTP adapter, and a switch to reach it

The public read port had one implementation and no way to add another. This is
the second one: the 18 operations of the public contract, mapped to the nine
methods the screens call.

The contract and the screens disagree about shape, and translating here is what
keeps the presentation components untouched. The server speaks in what it
stores — timestamps, one markdown body, relations grouped by why they relate.
The screens were built against a catalog that spoke in what a page renders —
formatted labels, titled sections, one flat relation list whose group name is
the reason. Neither is wrong. Where the contract has no counterpart the value is
left empty and the gap is named where it happens rather than guessed at: a
Case's verification line, a decision's consequences, a question's options.

Sections are split from markdown here rather than through the Studio parser.
That parser produces the canonical render-block union the editor needs — inline
marks, evidence directives, tables — which is a richer tree than RecordSection
can hold, so reusing it would mean flattening away exactly the blocks that made
it worth using.

A 404 is unwrapped, not thrown. A slug that is not published is an answer the
port already has a shape for, and throwing would put a terminal-error surface on
a page whose real state is "this does not exist".

`listRecords` is one method over two endpoints, because the contract pages and
filters knowledge separately from questions. Only the unfiltered call fans out:
asking for one kind must not pay for the other.

The operations declare the ANONYMOUS auth profile, which forbids credentials
outright. That is the point — a later change that starts sending the session
cookie on a public read fails the profile check instead of quietly making a
cache-friendly surface user-specific.

public/release-manifest.json

@@ -38,8 +38,15 @@
   },
   "contractSet": {
     "setAlgorithm": "CA_CONTRACT_SET_V1",
-    "setDigest": "sha256:5a67c3ce96f6be3a9314040f3039ca32a81f9eaf4402c88a745e235d183f23df",
+    "setDigest": "sha256:8ae48a17a30f07a0672fbc2c46ea9ebe66637bd16f6914079b3bf31b8009d12f",
     "packages": [
+      {
+        "packageId": "@tech-log/public-contract",
+        "version": "2.0.0",
+        "digest": "sha256:8ac71425b38658f34641102b4c2e6e21288c811efebdb92c0a46fb9d4790e23e",
+        "runtimeProtocolVersion": 1,
+        "sourceRevision": "55a9599"
+      },
       {
         "packageId": "@tech-log/studio-contract",
         "version": "3.0.0",