[zhaozhaozz]

What

Adds an interactive open-age donut chart directly above the open list on both the Issue and PR pages. On the Issue page it replaces the old non-interactive age-distribution bar chart; on the PR page it is new.

• Sectors are computed from the page's own open items with the same bucket boundaries as the collector's aging summary: <7d [0,7), 7-30d [7,30), 30-90d [30,90), >90d [90,∞). Items without age_days are not counted; zero-count buckets are listed in the legend but are not clickable. Legend entries show both the count and the share, and the selected sector/entry gets a clear selected state.
• Clicking a sector or legend entry filters only that page's open list — the table and the board view alike; clicking the selected one again clears the filter. The bucket combines (AND) with the existing search/label/assignee filters, and the Issue and PR selections stay independent. An active bucket shows up as a clearable chip in the filter bar and in the board toolbar.
• The side cards (recently updated, longest idle) and the recently-merged table are not affected; an empty result shows an empty state while the pie stays visible.
• Sectors are keyboard-operable controls (role=button, aria-pressed, Enter/Space) with accessible names; colors reuse the existing sequential palette, no new dependencies.

Implementation

• static/app.js: AGE_BUCKETS/ageBucketOf/agePie/ageChip helpers, per-page STATE.ageFilter, click and keydown delegation, the filter applied in renderIssues/renderPRs; helpers shared with the board via window.GSB.
• static/board.js: the board's filtered() applies the same per-scope age selection, the toolbar mirrors the active bucket as a chip, and “clear all” clears the age filter too.
• static/style.css: pie and legend styles on the existing palette; static/index.html cache version bumped.
• docs/dashboard-pages.md: feature description and browser-test coverage updated.

Tests

• New journey open-age pie filters only the open list on its own page in test/journey-board.spec.cjs covers bucket boundaries and counts, sector/legend clicks, re-click to clear, chip clearing, keyboard activation, intersection with the text search, empty results, Issue/PR independence, board-view filtering, and that the side tables stay unfiltered. The two existing assertions on the replaced bar chart now expect the new card.
• node .e2e/node_modules/playwright/cli.js test --config test/playwright.config.cjs → 24 passed, 1 failed; the failure (Real E2E cases show run marks…, .score-failed count) reproduces identically on the unmodified baseline tree, so it is pre-existing and unrelated to this change.