Add refresh button in webui and r/? keys in tui

[lsegal]

Summary

• Add a refresh button to the web dashboard, next to the settings button, that forces glorp to immediately repoll GitHub for issues instead of waiting for the normal poll interval.
• Add an "r" keybinding to the terminal dashboard that triggers the same immediate repoll.
• Add a "?" keybinding to the terminal dashboard that shows a help overlay listing all available keybindings (q/ctrl+c to quit, r to refresh, h/l or arrows to page agents, ? to toggle help).

Root cause / context

glorp already had an internal "poll now" mechanism (Glorp.nudgePoll, used for ownership handoffs), but nothing in either dashboard exposed it to an operator: they had to wait out the run's configured poll interval to see new issues picked up.

Change

• webui/server.go: new SetRefreshHandler + POST /api/refresh endpoint, mirroring the existing job-action/settings handler pattern.
• main.go: wires the webui and terminal-UI refresh handlers to w.nudgePoll().
• ui.go: adds TerminalUI.SetRefreshHandler/requestRefresh, an "r" key case that calls it, a "?" key case that toggles a centered help overlay (and swallows other keys while it's open), and a newDashboard(ui *TerminalUI) parameter so the model can reach back into the TerminalUI.
• webui/src/dashboard.js + main.jsx: a submitRefresh() helper and a refresh button (spinning ArrowPathIcon while in flight) beside the settings button.
• CHANGELOG.md: added an ## Unreleased entry.

Tests

• webui/server_test.go: refresh endpoint wiring, unavailable-handler 503, core.ErrNotReady handling, method rejection.
• webui/src/dashboard.test.js: submitRefresh posts correctly and surfaces errors.
• ui_test.go: "r" requests a refresh (and is a no-op when unwired), "?" opens/closes the help overlay and swallows other keys while open.
• go build ./..., go vet ./..., go test ./... all pass; pnpm test (67 tests) and pnpm run lint (biome) pass in webui/.

Screenshot

Terminal dashboard help overlay (text, since it has no animation):

                              Keybindings

                              q, ctrl+c   quit
                              r           refresh now (repoll GitHub)
                              h/l, ←/→    switch job page
                              ?           toggle this help

Closes #646

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