TODO-004: `:todo` meta-pair args — render, click, filter

Now: OPEN

Put the meta pairs to work in the ticket views: render Key: value rows nicely, make both halves clickable, and grow the :todo arg grammar so Key:Value filters are first-class args, answered through the TODO-003 index. Builds on the BE-038 board (:todo, :todo TOPIC, :todo TOPIC-123) and the TODO-001 board IO.

Input

Context

Meta pairs: StrictMark §"Meta pairs"; ticket keys (Now: Sev: Who: Due: …) registered in todo.
TODO-003 landed: metaidx.find(query, opts) is LAZY (scan, index the unindexed, answer) and returns {tickets:[{id,rel,code,file,mtime,meta}], sweep}.
The status migration has RUN: Now: carries the state and Sev: the priority, so the header [MARK] grep that views/todo/todo.js filters on is dead — 9 of 837 headers still carry a mark and the board lists closed tickets.
BE-038 landed the board shapes; TODO-002 adds progress badges; BE-040 the [done] buttons — this ticket must compose with those rows, not fork them.

Goals

The arg line is a topic OR a ticket id, plus any number of Key:Value filter args, in any order. Errors in plain words.

:todo — the board; :todo TODO — one topic; :todo TODO-004 — the page (all unchanged).
:todo Now:OPEN — one filter; :todo TODO Now:OPEN — a topic and a filter; :todo Who:gritzko Sev:HIGH — two filters, AND.
Repeat a key to OR it: :todo Now:OPEN Now:DONE. A second colon inside one token is an error in plain words, not a second meaning.
Now:* matches any value (presence); Now: matches not-defined-or-empty; a bare key with no colon is an error pointing at Key:*.
Lexical classes: [A-Z]+-[0-9]+ ticket id, all-caps word topic, Key:Value filter — case alone separates ABC from Ask:.
Ticket view renders meta pairs as a key–value block under the header; board rows may show a queried key's value inline.
A click REPLACES that key's filter and leaves the rest of the arg line alone: on :todo TODO, clicking OPEN gives :todo TODO Now:OPEN, and clicking DONE then gives :todo TODO Now:DONE.
The click spell carries the WHOLE arg line, not a todo(key, value) call — that is what makes replacement and the address-bar display expressible (BRO-025).

Constraints

Spaces and colons SEPARATE, so a filter value carries neither: Rev: and See: values (URIs, links) are presence-filterable only, never exact.
With no Now: in the query the board hides Now:DONE and Now:DONT ONLY — Now:STALE and pair-less tickets stay listed (fail-open, as an unmarked header used to).
Any mention of Now: overrides that default, so :todo Now:DONE reaches the closed tickets.
Filters go through TODO-003 find() only — values and titles for DISPLAY come from reading the narrowed tickets, never from the index payload (it is a despaced, decased match token, sometimes only a hash).
Sev: values order CRIT > HIGH > MED > LOW per todo; unknown keys and unknown values are legal args — the index is key-agnostic.
Reuse the TODO-001 read/memo path for titles+badges once it lands; until then do not build a second memo layer.

WIP

Design decisions

Time-sort is POSTPONED (ruling 2026-08-03) — until it lands, flat filter results order by topic+number and the board keeps its Sev: order.
When it does land: dirty tickets sort by mtime, committed ones by last-commit time, dirty first.
mtime alone cannot carry freshness — a checkout restamps every file, so in a fresh clone all 837 tickets tie (measured: a 12:32 clone stamps every file 12:32:07).
Nor can the walk run per render: be list todo costs 2.8 s and still leaves entries unk at the LIST_MAX_WALK ceiling, against 17 ms for a warm index query.
The shape that works is ONE newest-first pass attributing every ticket (shared/lastcommit.js), bounded to the visible rows, cached against the tip — never the per-file weave walk repeated down the list.
Tickets lacking a queried key list after those having it rather than vanishing — filters hide, sorts never do.

TODOs

arg lexer: topic / ticket id / Key:Value filters, repeat-key OR, Key:* and Key: forms, plain-word errors
the implicit Now: default (hide DONE + DONT) and its override
filters through TODO-003 find(); value+title read-back over the narrowed set
ticket view: meta block render, key/value clicks that replace one filter in the whole arg line
board rows: queried key's value inline, composed with TODO-002 badges
golden: each arg form, OR and presence forms, click replacement round-trips, the Now: default and its override
time-sort, once unpostponed (its own ticket)

Blockers and bummers

TODO-003 has landed; the SPOT-003 dependency it carried is gone.
verbs/done/done.js writes a header [DONE] mark, not Now: DONE, so the pair and the header can drift — its own ticket.

TODO-004: :todo meta-pair args — render, click, filter