feat(web): 2x reading column on wide desktops — 92rem at >=1500px (chat, shared, document view)

frontend/assets/styles.css

@@ -33,6 +33,11 @@
   --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
 
   --header-h: 64px;
+
+  /* Reading column: 46rem base (PLAN §7 lineage); 2x on wide desktops
+     (owner instruction 2026-08-31, TODO L5 / D2 — chat + shared +
+     document view). */
+  --chat-column: 46rem;
 }
 
 * { box-sizing: border-box; }
@@ -394,9 +399,11 @@ html::after {
 
 /* Chat is a vertical conversation: a centered, capped column is the
    correct layout here (PLAN §UI/UX). The surrounding frame keeps it
-   from collapsing into a hairline on wide screens. */
+   from collapsing into a hairline on wide screens. The cap is the
+   --chat-column token: 46rem base, 2x (92rem) at >=1500px wide
+   desktops (owner instruction 2026-08-31, TODO.md L5 / D2). */
 .chat-shell {
-  max-width: 46rem;
+  max-width: var(--chat-column);
   margin-inline: auto;
   display: flex;
   flex-direction: column;
@@ -413,8 +420,9 @@ html::after {
    on desktop. The ≤640px block flips this to a vertical stack
    (flex-direction: column + align-items: stretch — full-width pills,
    New chat above Share; the existing ≤640px pill rules apply to the
-   stacked pills unchanged). The 46rem column contract is untouched
-   (PLAN §7). */
+   stacked pills unchanged). The reading-column contract is untouched
+   (--chat-column: 46rem base, 92rem at >=1500px — PLAN §7 lineage).
+   */
 .chat-actions {
   display: flex;
   flex-direction: row;
@@ -493,7 +501,8 @@ html::after {
 /* GFM pipe tables (phase 44, 2026-08-27, TODO.md L6): the shared
    renderer wraps every table in .md-table-wrap — the horizontal
    scroller, so a wide table scrolls inside the bubble instead of
-   breaking the 46rem column — around a semantic <table class="md-table">
+   breaking the reading column (--chat-column: 46rem base, 92rem at
+   >=1500px) — around a semantic <table class="md-table">
    (escape-first cells; alignment colons render left, owner decision).
    Phase-08 tokens only: --line hairline borders and the thead tinted
    from the plain surface family — --ink on --surface is 14.5:1 (PLAN
@@ -590,9 +599,9 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
    own icon, own accent left border. Contrast: --accent-ink on the row's
    --surface ≈10.4:1 (11.6:1 on the page bg), and --ink on --brand-soft
    in the path `code` ≈11.5:1 — all comfortably AA in the (single dark)
-   theme. Inline rows only: appending lines never shifts the 46rem chat
-   column (no new container), and the rows are not interactive — no
-   focus targets. */
+   theme. Inline rows only: appending lines never shifts the chat
+   column (46rem base; 92rem at >=1500px — no new container), and the
+   rows are not interactive — no focus targets. */
 .tool-calls {
   display: flex;
   flex-direction: column;
@@ -1144,7 +1153,8 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
 /* ---------- Composer ---------- */
 /* Phase 52 (2026-08-30, TODO.md L3): the composer is PINNED to the
    viewport bottom. The page scrolls at the document level and
-   `.chat-shell` (the centered 46rem column) is the composer's sticky
+   `.chat-shell` (the centered reading column — 46rem base, 92rem at
+   >=1500px) is the composer's sticky
    containing block, so the box sticks to the bottom edge of the
    viewport at every scroll position and settles back into its normal
    flow position (above the footer) once the document bottom is
@@ -2138,7 +2148,8 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
 /* ---------- Shared page (phase 51, task 03) ----------
    /shared/<token>: the anonymous read-only conversation (owner-locked
    2026-08-29, TODO.md L6). The shell maps to the PLAN §7 centered
-   46rem chat column — the conversation reads exactly like the chat
+   chat column (--chat-column: 46rem base, 92rem at >=1500px) — the
+   conversation reads exactly like the chat
    page (the .msg/.bubble/.thinking/.tool-calls/.msg-meta rules apply
    unchanged) with NO composer, so the column contract holds for a
    guest. Zero interactive controls (owner-locked): the chips are
@@ -2150,7 +2161,8 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
    fonts. */
 .shared-shell {
   width: 100%;
-  max-width: 46rem; /* the PLAN §7 centered chat column */
+  max-width: var(--chat-column); /* the PLAN §7 centered chat column
+     (46rem base; 92rem at >=1500px — phase 58) */
   margin-inline: auto;
   display: flex;
   flex-direction: column;
@@ -2313,10 +2325,12 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
 #doc-content { display: flex; flex-direction: column; }
 .doc-loading { margin: 1.5rem auto; text-align: center; color: var(--ink-soft); }
 
-/* Markdown: the centered, ≤46rem reading column (PLAN §7.1). */
+/* Markdown: the centered reading column — 46rem base, 2x (92rem) at
+   >=1500px (PLAN §7.1 lineage; owner instruction 2026-08-31, TODO.md
+   L5 / D2). */
 .doc-md {
   width: 100%;
-  max-width: 46rem;
+  max-width: var(--chat-column);
   margin-inline: auto;
   background: var(--surface);
   border: 1px solid var(--line);
@@ -2361,12 +2375,13 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
   margin-bottom: 1rem;
   overflow-wrap: anywhere;
 }
-/* md/markdown: the panel matches the .doc-md ≤46rem centered reading
-   column — it is the column's label. Raw formats stay full width (the
+/* md/markdown: the panel matches the .doc-md centered reading column
+   (46rem base; 92rem at >=1500px — the same --chat-column token) —
+   it is the column's label. Raw formats stay full width (the
    .doc-raw default above), matching the full-width pre; in engines
    without :has() the panel degrades to that full-width default. */
 .doc-summary:has(+ .doc-md) {
-  max-width: 46rem;
+  max-width: var(--chat-column);
   margin-inline: auto;
 }
 .doc-summary-title {
@@ -2528,7 +2543,8 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
 /* ---------- Document modal (phase 26) ----------
    "New documents should open in an almost-fullscreen modal, not in a new
    page" (TODO.md L4). The overlay reuses the viewer page's .doc-meta
-   badge classes, the .doc-md ≤46rem reading column, and the .doc-raw
+   badge classes, the .doc-md reading column (46rem base; 92rem at
+   >=1500px), and the .doc-raw
    pre — this block only adds the chrome (backdrop, panel, header,
    actions, scroll container). Phase-08 tokens only; NO blur (the
    phase-08 no-blur perf anchor); no new assets; system fonts.
@@ -2667,7 +2683,8 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
 }
 
 /* The scroll container: vertical scroll lives HERE, never the viewport.
-   .doc-md keeps its ≤46rem centered reading column inside; .doc-raw keeps
+   .doc-md keeps its centered reading column inside (46rem base;
+   92rem at >=1500px, capped there by the 1100px panel); .doc-raw keeps
    its own overflow-x. tabindex="-1" in the markup is the JS focus target. */
 .doc-modal-content {
   flex: 1;
@@ -2951,8 +2968,9 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
   .history-actions { flex-wrap: wrap; }
   /* Phase 51: the shared page squeezes like the chat column — the
      title and the note step down (the empty-state-title family); the
-     shell keeps its 46rem column (it is already the narrowest box on
-     the page) and .msg-body's 92% override above applies. */
+     shell keeps its base 46rem column (the >=1500px 92rem override
+     never applies here — it is already the narrowest box on the
+     page) and .msg-body's 92% override above applies. */
   #shared-title { font-size: 1.35rem; }
   .shared-note { font-size: 0.88rem; }
   .footer-inner { flex-direction: column; gap: 0.2rem; text-align: center; }
@@ -2973,6 +2991,24 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
   }
 }
 
+/* Phase 58: wide desktops (viewport >=1500px) read the 2x column —
+   --chat-column doubles to 92rem for the four reading shells (chat,
+   shared, the document viewer's .doc-md and its summary panel). The
+   chat and shared shells ARE their .container (the token max-width
+   overrides the .container's 72rem cap — same specificity, later in
+   the file), but the document page's .container.doc-shell WRAPS the
+   column, so the 72rem cap would bind first and pin .doc-md at
+   ~1112px: the wide block lifts the shell's cap to the column plus
+   the container's two 1.25rem gutters, letting .doc-md's own 92rem
+   cap bind (1472px at the 16px root). Everything below 1500px
+   renders exactly as before, and .tuning-shell (a form, not a
+   reading surface) keeps its hard-coded 46rem at every width
+   (owner instruction 2026-08-31, TODO.md L5 / D2). */
+@media (min-width: 1500px) {
+  :root { --chat-column: 92rem; }
+  .doc-shell { max-width: calc(var(--chat-column) + 2 * 1.25rem); }
+}
+
 /* Phase 46: prefers-reduced-motion stills the mobile menu — no
    180ms slide+fade; open/close snaps (the visibility/opacity flip
    applies instantly) and stays correct. BOTH states are named: the