Projects: classes as entities, and the sidebar fits short windows

A project is a class with facts (description, status, kind, party,
dates, links, notes) in one project.set event behind the format
feature projects. Four tools (books.add_project, update_project,
projects, project); documents and decisions link to projects; B-37:
on-spec costs are expensed as incurred, repayment is revenue, and the
unrecovered cost is never below zero (Kani). Viewer: a Projects list
and a project page with its figures, by month and by account. The
sidebar measures its footer instead of reserving a fixed 172 px.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-gui/tests/kept.rs

@@ -116,6 +116,7 @@ fn the_company_page_shows_how_the_books_are_kept() {
             evidence_attachment: None,
             supersedes: None,
             citation: None,
+            projects: vec![],
         })
         .unwrap();
     s.record_decision(&NewDecision {
@@ -126,6 +127,7 @@ fn the_company_page_shows_how_the_books_are_kept() {
         evidence_attachment: None,
         supersedes: Some(first),
         citation: None,
+        projects: vec![],
     })
     .unwrap();
     s.raise_open_item(&item("Mail the IRS letter", Some(d(2026, 10, 16))))