feat(web/beads): close reason in Comments tab; synthesize subtask-add history

- Close reason placement: show it as a block at the end of the Comments tab
  (which carries no closed event), while the History tab shows it inline as the
  closed event — so it appears in whichever tab you're on, without duplication
  within a tab. (Reverts the outright removal.)

- History now includes dependency/subtask additions. beads logs no audit event
  for a link, but the dependencies row records created_at/created_by, so
  buildDetail synthesizes "added subtask X" / "added dependency on X" timeline
  entries (Kind "dep", own accent). On an epic this surfaces when each child was
  linked. Guarded on created_at so older schemas without it emit nothing.

- pre.field-body style de-scoped from .bead-detail so the Comments-tab close
  reason wraps (overflow-wrap: anywhere) instead of overflowing.

refine(web/beads): concise label events, drop standalone close reason, wrap long lines

- Label audit events collapse to one line ("added label milestone:m3") instead
  of a "label added" header plus a redundant "Added label: …" body. The label
  name is taken after the first colon so namespaced labels survive.
- Remove the standalone Close reason block below the activity: the reason
  already shows as the History tab's `closed` event, so it was a duplicate.
- Add overflow-wrap: anywhere to the timeline body, comment body, and
  field-body pre so a very long single-line reason wraps instead of overflowing.

feat(web/beads): epic view with subtask rollup, tabbed Comments/History

Three additions to the beads issue detail:

- Epic mode: when the viewed issue is issue_type=epic, render a Subtasks panel
  — its parent-child children (deps pointing at the epic) with a done/total
  progress meter, sorted open-work-first with closed sinking to the bottom.

- Activity is now a two-tab strip (pure-CSS, no JS): Comments keeps the plain
  thread; History merges comments and the audit-log events table into one
  time-sorted timeline with humanized change lines ("changed status to
  in_progress", "updated priority to 0", "closed the issue" + reason).

- Close reason moved from the top metadata table to its own block at the very
  bottom, after the activity — it reads as a closing note, not a header field.

Verified end-to-end against a real 143-issue beads store (tarantool-etcd) via
the env-guarded TestRealBeadsStore smoke test; unit-covered with a dedicated
epic/history fixture.

feat(web): Overview/Tables/Beads tab bar + full issue fields on beads detail

Give every database page a consistent three-tab bar — Overview, Tables,
then the applicable views (Beads) — in that order. Previously the bar only
carried [views, Tables] and the Overview page marked Tables active, so there
was no way to tell you were on the overview. viewtabs now takes an explicit
Current sentinel ("overview" | "tables" | view slug) and the tree/table row
pages render the bar too (handlers compute applicable views for the ref).

Surface the issue fields the beads detail pane was dropping. The closure
reason (close_reason) recorded by `bd close -r` was never shown; auditing
against bd's own field set also turned up estimated_minutes, external_ref,
spec_id, and started_at. All render conditionally, so issues that don't set
them stay uncluttered.

style(web): restyle the beads parade in the todo.sr.ht idiom

The board still read as a rounded-card kanban from another app. Re-skin
every surface in sourcehut's own issue-tracker language (todo.sr.ht):
flat and square — no border-radius, no shadows, no tints — hairline gray
borders, monospace ids, striped-on-hover rows instead of cards, and
squared bordered labels (the sourcehut .label: 1px border, no radius).
The summary becomes a flat hairline strip and each lane a squared column
with a 2px accent cap. The Mardi Gras hues survive only as small square
swatches and the lane cap, never as fills, so the view looks like a
native sourcehut tracker in both the light and dark themes. Verified via
a headless light/dark render. Test asserts the renamed summary class.

fix(web): make the beads view inherit the SourceHut theme

The beads board shipped its own Mardi Gras palette — a purple→green
marquee gradient and saturated solid lane fills — that clashed with
SourceHut's flat, utilitarian dark theme, and the detail pane's field
labels were a hardcoded dark purple with no dark-mode override, leaving
"Created by / Owner / Description" unreadable on the dark background.

Drive everything from CSS variables that mirror core.sr.ht's Bootstrap
palette for both the light default and the prefers-color-scheme: dark
variant sourcehut ships (the same media query it uses), so the view
inherits the host theme instead of fighting it. Lane hues become muted
Mardi Gras accents (gold/green/violet/gray) used only as thin borders and
low-alpha tints — never as body text — so contrast holds on either theme.
The marquee is now a flat stat row, lanes an understated panel with an
accent underline, and detail labels a readable muted caption. Verified
light and dark via a headless render.

feat(web): Mardi Gras beads view

Render a beads (bd) issue database as a Mardi Gras parade board: four
lanes — Rolling (in progress), Lined Up (open & ready), Stalled (open &
blocked), Past Stand (done) — plus a marquee of per-lane counts. Cards
show id/title/type/priority/assignee/labels and blocked-by/blocks counts;
an issue-detail pane (?issue=<id>) shows the full issue with its
dependency edges in both directions and its comments thread.

Fingerprints on the issues + dependencies tables and reads everything
through the browse layer (column-name-keyed, so column order is
irrelevant), capped at 2000 rows/table. Status is bucketed via
custom_statuses with name heuristics as a fallback; "blocked" means
is_blocked or an open blocking dependency. Plugs into the view registry
via init()+RegisterView with no framework edits. Purple/gold/green
palette scoped in the template (no scss rebuild needed).