docs(concepts): add Wiki retrieval pillar page (#191)

* docs(concepts): add Wiki retrieval pillar page

Adds a dedicated concept page covering the wiki side of the context
layer: the page contract, the hybrid retrieval pipeline (lexical,
semantic, token lanes fused by RRF), the refs/sl_refs/[[wikilink]]
graph, validation that keeps edges live, and where ingest sources
pages. Wired into concepts nav and cross-linked from the-context-layer
to mirror the existing Semantic querying link.

* test: derive release versions in tests instead of hardcoding 0.1.0-rc.1

After @semantic-release/git started committing version bumps back to the
branch, the 0.4.0 release rewrote package.json, packages/cli/package.json,
and release-policy.json — but the script and CLI tests still pinned the
pre-bump strings (0.0.0-private, 0.1.0-rc.1, 0.1.0rc1), so every new
branch off main failed TypeScript checks and Coverage.

Drive the version off the existing source of truth instead: read
@ktx/cli/package.json via createRequire in the CLI tests, and reuse the
already-imported PUBLIC_NPM_PACKAGE_VERSION / RUNTIME_WHEEL_PACKAGE_VERSION
constants in the script tests. The two assertions that pinned those
constants to specific values become semver shape checks.

docs-site/content/docs/concepts/meta.json

@@ -1,5 +1,5 @@
 {
   "title": "Concepts",
   "defaultOpen": true,
-  "pages": ["the-context-layer", "semantic-layer-internals", "context-as-code"]
+  "pages": ["the-context-layer", "semantic-layer-internals", "wiki-retrieval", "context-as-code"]
 }