Build "Is it alive?" signal section

[rigomart]

Part of #82

Depends on: #83
Blocks: #89

Summary

Create a unified "Is it alive?" section that combines and reframes the current Recent Activity timeline and Commit Activity chart into a single cohesive section focused on answering whether the project is actively maintained.

What changes

Currently this data is split across two separate sections:

• Recent Activity — a scatter plot timeline + 4 cards showing last commit, last release, last issue closed, last PR merged
• Commit Activity — a weekly commits line chart over the past year

These get merged into one section under the "Is it alive?" framing. The section should present:

• Activity timestamps — last commit, last PR merged, last release, last closed issue, each as plain dates with relative time
• Commit trend — the existing weekly commit chart, showing whether activity is stable, growing, or declining
• Overall activity pattern — whether the project shows consistent activity or has gaps

The data for all of this already exists in the metrics snapshot. This is a reorganization and reframing, not new data collection.

Acceptance Criteria

• A single "Is it alive?" section replaces the separate Recent Activity and Commit Activity sections
• All four activity timestamps (commit, PR, release, issue) are displayed with absolute + relative dates
• The commit trend visualization is preserved (weekly chart)
• The section reads as a cohesive answer to "is this project still active?"
• The existing scatter plot timeline is either integrated or replaced with something that serves the same purpose within the new framing

[rigomart]

Superseded by the new three-layer direction in #82. The "Is it alive?" narrative section is replaced by the Development Activity dimension (to be defined).