tui: combine status bar's page/web/id onto one line

[lsegal]

Summary

Fixes the terminal dashboard's status bar layout reported in #647.

Before, the pager hint and web link each sat on their own bare, unstyled line below the status bar, separated from it and each other by a blank gap line, and the instance id shared the first (colored) line with the job counts.

Now:

• The page indicator and web link share a single status-bar-styled line, directly under the job counts line, with no blank gap above it.
• That line carries the same colored background style as the counts line above it, instead of rendering as plain unstyled text.
• The instance id moves down onto that second line (leftmost), freeing the counts line for jobs/quota/polling/targets.
• The web link is underlined and its label is shortened from "web dashboard" to "web".

Rendered output (colors stripped for the text capture, background/underline verified separately in tests):

 jobs: 1 idle 2 active 3 total  quota: weekly 87% left  polling every 20s  targets: lseg...
id: E14717D0 page 1/3  ←/→ (or h/l) for more agents  web: http://localhost:8765

Changes

• ui.go: fuse the id/pager/web cells into one status-bar-styled line (renderStatusInfoLine), reusing renderStatusBar's cyclic cell coloring; underline the web link with a style matching its cell's background/foreground (underlineSpanStyle), since a nested Lipgloss span resets its parent's style; adjust jobsPerPage/visibleJobs chrome accounting now that the info line no longer costs its own gap line.
• ui_test.go: update tests for the new id placement and "web:" label, add tests for the merged/gap-free line and the underline span style.
• CHANGELOG.md: add an unreleased entry.

Tests

• go test ./... passes.
• go vet ./... and gofmt -l . are clean.

Closes #647

Agents: claude-code (claude-sonnet-5)