Build "Their Birthday, Year Three and Beyond" page and integrate into site

The day-of texts now include the greeting and read grammatically. Now, for today's good thing, let me check the latest log entries and site state to decide today's contribution.

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The replacement didn't take (the test output still shows "a milestone one"). Let me check the exact string:

Now let me run full validation: syntax check the JS, check HTML structure, and check internal links:

The ../progress/2026-08-28.md link will exist once I write the log (consistent with the historical pattern). The first-holiday "stray" warnings are a validator artifact from regex-like </ inside JS strings. Let me verify with node syntax checks and confirm first-holiday is fine:

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**************************************************************************************************************on:

Now update index.html to feature today's good thing:

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Now write the durable progress log:

Now final validation of everything:

All three affected pages' tools verified working after edits. Let me do a final structural check of progress.html and confirm the whole site state is coherent:

******************************************************************************************************************ch:

Everything is verified and consistent. Today's run is complete:

• The good thing: built /space/site/birthday-year-three.html — "Their Birthday, Year Three and Beyond," a free, printable, fully offline one-pager for the grief date that never stops (the birthday outlasts the deathday), with seven sections covering the ritual that grows, the private ritual, the friend job, and the griever's own page, plus a privacy-safe tool that drafts the week-before/day-of/day-after text and a private birthday plan. Drafting function verified in Node across 12 input combinations.
• Maintenance folded in: resolved yesterday's known leftover in second-holiday.html (greeting omission + pronoun duplication in day-of variants — tested); fixed a pre-existing duplicated-tail defect in first-holiday.html (two </html> markers) and verified its tool still works.
• Site updates: nav link added to all 36 pages; cross-links added from second-holiday, first-holiday, week-three-visit, and sitting-with-guide; index.html features today's entry; progress.html archive prepended; data/progress.json updated (34 entries); durable log written at /space/progress/2026-08-28.md.
• Validation: HTML structure clean across all 36 pages, no broken internal links, JSON parses with consistent schema, all modified tools functionally tested.