simulate: open a cited turn from the summary with its number

[u9g]

Stacked on #939 — base it there, and the diff is this one commit.

A summary citation could only be followed out of the terminal, by ctrl+clicking
its OSC 8 link into the dashboard. The turn it cites is already in the run, so
the TUI can open it directly.

Each citation now renders as "quoted text" [3], and pressing that digit on the
list view opens the cited job. The hint line gains 1-9 cited turn when a
summary has citations. The OSC 8 link stays, so ctrl+click still reaches the
dashboard — both work.

Notes on the design

Numbering is derived during render, not in a second pass. One index is
threaded through every block of the summary, and renderSummary stores its
targets at the end. Collecting the citations separately would be a second source
of truth that could drift from the labels; this way the digit a reader presses
and the label showing it cannot disagree.

A citation is numbered when it names a job, not when a dashboard URL
resolves. The jump is local, so it works where the link does not — previously
an empty simulationItemDashboardURL degraded a citation to bare text, which
would have disabled the keyboard jump along with the link. One existing test's
contract changed to document the split: no job → plain text; job but no URL →
numbered, no hyperlink.

Only the first nine are numbered. A number is an invitation to press that
digit, and there is no tenth. Citations past nine stay hyperlinked for
ctrl+click.

The cited turn is marked where it prints. A jump lands at the top of the
printed job, and scrollback cannot be scrolled to the citation, so the turn says
◀ cited. The mark rides the message text rather than the speaker header: a
message continuing an open agent block never prints a header, which is exactly
the turn a tool-heavy run tends to cite.

Why keyboard and not ctrl+click

Intercepting the OSC 8 link itself is not possible — the spec defines no channel
for reporting activation to the application, and kitty's open_actions only
launches a separate external program. Capturing a raw ctrl+click is possible,
but it needs mouse reporting enabled, which takes the mouse away from the
terminal and puts native drag-to-select behind shift. runSimulateTUI opts out
of mouse capture deliberately ("No mouse capture, so the terminal keeps native
drag-to-select"), and #928 moved the job view into scrollback precisely to give
the terminal back selection and search. The digits cost none of that, and work
over a mouse-less ssh/tmux path.

Testing

go test ./cmd/lk/ passes, covering the numbering, the no-job and no-URL
degradations, and the nine-citation cap. go vet and gofmt are clean.