Add requirements seed from yawex prior-art review

Distill the yawex-0.7.4 Perl wiki engine into shard-wiki requirements:
KEEP federation-relevant ideas (page-resolution state space as inspiration,
namespace hierarchy, page/shard roles, derived views, provenance, blueprints,
overlay/append, multi-shard config), TRANSFORM markup to CommonMark + wikilink
extension, DROP engine/era artifacts. Flags a contested decision: a minimal
access model in core revises an INTENT non-goal and needs an INTENT amendment.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/requirements-from-yawex.md

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+# Requirements seed — review of yawex prior art
+
+Source: `history/priorart/yawex-0.7.4/` — a filesystem-backed CGI/Perl wiki engine
+(2004–2005, "Yet Another Wiki engine eXtended"). This document distills that prior
+art into requirements for `shard-wiki`, the Markdown-first, Git-backed wiki
+**federation/orchestration layer** described in `INTENT.md`.
+
+Each item is tagged **KEEP** (adopt the idea), **TRANSFORM** (keep the intent, change
+the mechanism), or **DROP** (engine/era artifact or INTENT non-goal). Decisions below
+reflect a review discussion on 2026-06-08.
+
+---
+
+## Orientation: what yawex was
+
+- Pages = plain files on disk. **Topics = directories.** A topic's "gateway" page
+  shares the directory name (`SubContext/SubContext`).
+- One CGI/Perl binary did everything: routing, page resolution, markup rendering,
+  auth, templating, storage.
+- The most-developed and most-tested component is **`PageLookUp`** — a context-relative
+  page-resolution state machine. It is the part most worth mining.
+
+---
+
+## KEEP — ideas that prefigure federation
+
+- **Page-resolution state space.** yawex resolved a requested name from a current page
+  through ordered states: `LOCAL, CLIMB, DROP, GLOBAL, REMOTE, SWITCH, JUMP, VIRTUAL,
+  FAILED`. Two states foreshadow federation directly:
+  - `REMOTE` — "jump to pages in a remote wiki" → a **remote shard**.
+  - `VIRTUAL` — "process locally but get content elsewhere" → a **projection / cache**.
+  - **Decision (2026-06-08): _inspiration only_.** Do NOT inherit yawex's structure as
+    the resolve contract. Design shard-wiki resolution fresh for the federation case;
+    treat these states as prior art and a checklist of cases the new resolver must
+    handle, not as the interface.
+- **Topic = namespace hierarchy** with relative (`../`) and absolute (`/`) paths, plus
+  path normalization. Becomes the union path/namespace model across shards.
+- **Page classes (local / global / virtual).** Map to **shard roles**
+  (canonical / cross-cutting / projected-computed).
+- **Derived/computed views**: BackLinks, RecentChanges, AllPages, SiteMap, full-text
+  Search. Natural **union-level views** over the federated page graph; BackLinks
+  (link-graph) is squarely shard-wiki's concern.
+- **Provenance hooks.** `Page::info` exposed modtime and TODO'd last-editor/hits/edits.
+  Serves INTENT's explicit-provenance-and-freshness principle.
+- **Blueprint pages** — create-from-template, duplicating topic structure. A
+  page/topic templating primitive.
+- **Append/comment workflow** — add to a page without a full edit. Maps to the
+  **overlay / lightweight-patch** model for shards you don't fully own.
+- **Multi-wiki config** (`Conf::TestWiki / FriendsWiki / ManusysWiki`). Literally
+  multiple distinct wikis with their own storage/identity = **multiple shards/roots**.
+
+## TRANSFORM — keep intent, change mechanism
+
+- **Markup → CommonMark + extension.** yawex had CamelCase WikiLinks, `[[free links]]`,
+  red-`?` links for nonexistent pages, `::` labels, `**bold**`. Keep the *semantics*
+  (auto-link, link-to-nonexistent) as a wikilink/red-link Markdown extension; drop the
+  bespoke syntax. INTENT mandates Markdown-first.
+- **Backup-on-write → Git history.** The `page~` rename hack becomes Git commits. Keep
+  the recoverability intent.
+- **Render pipeline → mostly out of scope.** The chunk+line renderer is engine/UI work.
+  Keep only the **link-resolution / normalization** slice that federation needs.
+
+## DROP — engine/era artifacts and non-goals
+
+- CGI/Perl runtime, Makefile install, `eval("action_$x")`, shell-outs (`rm`, `htpasswd`,
+  `echo >`), `umask 0000`, `fatalsToBrowser` — implementation and security debt.
+- JS editor toolbar / textarea editor — UI layer; INTENT decouples UI from storage.
+- Form chunks (`Formular` + KEY= data store) and Blog chunks — app-specific page
+  semantics that INTENT says core must not own.
+
+---
+
+## Contested decision: a minimal access model IN CORE
+
+yawex coupled identity and permissions into the engine: Apache/htpasswd auth, a members
+file, self-registration with auto-created user pages, and per-topic `AccessControl` files
+with levels `denied / view / form / edit / admin`.
+
+INTENT.md currently lists this as a **non-goal**: *"Solve organizational permissions,
+identity management, or secret storage by itself."*
+
+**Decision (2026-06-08): shard-wiki WILL own _some_ auth in core** — a deliberate
+revision of that non-goal. Proposed tight scope so it doesn't become an identity system:
+
+- **In scope:** a thin, pluggable **authorization gate** expressed as capabilities —
+  who may read / write / patch / merge a given page or shard — layered on top of the
+  per-adapter capability model (read/write/diff/merge/lock/publish).
+- **Out of scope (still):** credential storage, organizational identity management, user
+  directories. Identity is supplied by a pluggable provider; shard-wiki authorizes, it
+  does not authenticate-from-scratch or store secrets.
+
+> ⚠️ **This revises an INTENT non-goal and therefore needs an INTENT amendment plus a
+> ratified decision** (per INTENT's Stability Note, redefining scope is an architectural
+> change). Tracked as an open decision; do not treat the access model as settled until
+> INTENT is updated.
+
+---
+
+## Open questions for the next pass
+
+1. Exact boundary of "some auth in core" — is per-page ACL in scope, or only per-shard?
+2. Does the wikilink/red-link extension belong in shard-wiki core, or in a reference UI?
+3. Which derived views (BackLinks / RecentChanges / Search) are core vs. adapter-provided?