Wikis with tens of thousands of pages used to crash the browser trying
to render the entire link graph at once (30MB+ JSON, 100k+ SVG elements).
This change moves the graph viewer from "fetch everything, render
everything" to "fetch a slice, expand on demand" with several matching
UX improvements.
Backend
* GET /wiki/graph now accepts `mode` (overview | ego), `center`, `depth`,
`types`, `limit` query params. Default is overview top-500 by
link_count, capped at 2000. Response includes a Meta object so the
frontend can render a truncation hint and drive the UI.
* Pure helper `computeGraphSubset` extracted for testability; six unit
tests cover overview truncation / type filter / ego BFS / missing
center error.
* WikiLintService passes Limit=0 (uncapped) so link integrity checks
still walk every page.
* Repo `Search` adds CASE-based relevance ranking (title 4, slug 3,
summary 2, content 1) so full-text results put the most obvious
matches first instead of whatever was updated most recently.
Frontend
* Graph viewer fetches overview on entry; ego pivot on double-click,
search, wiki-link click, URL ?slug=, global issues jump.
* Shift+click or hover ⊕ button blooms neighbors onto the current
canvas additively. Bloom tracks generations and LRU-evicts oldest
when total exceeds 1500 nodes; ego center / selected node / latest
anchor are always protected.
* "Grow frontier (N)" legend action expands every dashed-ring node in
one click (6-way concurrency) while skipping Index/Log super-nodes
that would otherwise dump the whole wiki onto the canvas.
* Node dashed expansion ring + drawer "X/Y neighbors shown" hint tell
users which nodes still have neighbors to load.
* Search dropdown uses remote full-text search (debounced, sequence-
numbered to drop stale responses) and falls back to the overview
top-500 snapshot when the input is empty.
* Type filters now round-trip to the server so top-N is always
computed from the user's active type set rather than hiding nodes
client-side and shrinking the view.
* Status card replaces the cramped "centered on X · N hops · M nodes"
line with a structured focus/overview summary, resolving slugs to
page titles.
* Help popover in the legend lists every canvas shortcut.
i18n entries added for zh-CN / en-US / ko-KR / ru-RU.
wizardchen
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