roadmap.md has become the journal its own header says the issues are for: decide what it is, and move the history #577

What the file says it is, and what it is

docs/roadmap.md opens: "This file is the shape of the work — what is outstanding, and why it is in this order. Whether a thing is started, blocked or done is on its issue. Two places holding the same checkbox is how a checkbox stops being true."

It is 2,791 lines. Everything still to buy carries eleven dated paragraphs — 2026-09-11, 09-13 twice, 09-17 twice, 09-18, 09-19 twice, 09-20 — narrating each purchase, arrival and fit, before the table they describe. The Infrastructure entry for #92 runs to some sixty lines and includes the wrong-account bug, the .part fragments and the zsh glob. The #102 entry is longer. Every one of those sentences was true and worth writing on the day; together they are the journal the header says the issues are for, kept in the one file that promised not to be one.

Two costs, both already paid once:

• Drift. docs(roadmap): six sentences the last week made false, and three residuals given their issue numbers #536 fixed "six sentences the last week made false" in this file; docs(roadmap): smaug is built and the pool is not #487 and docs/roadmap.md still says smaug is unconfigured and its firewall rules unwritten #486 fixed more the week before. Dated narrative goes stale by construction, and check_docs.py can count claims but cannot read a paragraph.
• Legibility. A reader who wants the shape of the work — the header's promise — reads past a month of purchase history to find it. The milestones on GitHub now carry that shape (seven, each with a close condition), which the file predates.

What to decide

• What the file is for, in one sentence that the header can keep: the ordered shape of open work, or the estate's changelog. Not both.
• Where the history goes if it leaves: a docs/changelog.md in the same voice, the ADRs' own dated notes (many of these paragraphs are amendments in all but location), or the closed issues, which already hold most of it verbatim.
• What a roadmap entry is allowed to contain once the file is the shape: a link, the gate, the order, and why — and the rule that a Done entry moves rather than accretes.
• Whether the Everything still to buy section survives at all now that the buy table is two rows and check_buy_list ties it to the README.

Done when

The header's sentence is true of the file below it, the history it carried is findable somewhere with a date, and the file is short enough that the next drift fix is one line rather than six.

Refs #536, #487, #486. Documentation only; no host changes.