First slice of the unified procedural-events tool train. Ships only the
page chrome — route, sidebar/header, filter strip with search box, four
entry-mode tabs (Verfahren wählen / Direkt suchen / Geführt / Aus Akte),
and the host containers later slices mount their UI into. No data wiring.
Per m's decisions (design §11.5): URL is English (/tools/procedures, not
/tools/verfahren); all four tabs visible from boot (not a single-default
landing); search box lives in the top filter strip and will compose with
chip filters once U1+ wire them.
U1 fills #procedures-panel-search (Mode A), U2 fills -wizard (Mode B),
U3 fills -proceeding + #procedures-output-tree (Verfahrensablauf), U4
hard-cuts /tools/fristenrechner and /tools/verfahrensablauf to 301
redirects and drops the legacy pages.