fix(home): hide Streamlit's chip row, keep only the canonical file list

After upload, two near-identical file lists were shown stacked:
Streamlit's built-in compact chip row inside the dropzone (icon +
``messy_sales.csv`` + size) and the home page's own "Uploaded files"
section beneath it (filename + Remove button). User flagged the
duplication.

Hide ``[data-testid="stFileChip"]`` and its first-child wrapper so
the chip row collapses; the dropzone's borderless ``+`` button is
preserved as the "add more files" affordance, and our "Uploaded
files" list is now the single source of truth visually.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gui/components/_legacy.py

@@ -346,6 +346,15 @@ body, .stApp {
     border: 1px solid var(--dt-border) !important;
     border-radius: var(--dt-r-sm) !important;
 }
+/* Hide Streamlit's built-in compact file-chip row once files exist —
+   the home page renders its own canonical "Uploaded files" list with
+   a Remove button beneath the uploader, so the chip row is redundant
+   and visually doubles up on filenames. The dropzone's borderless
+   ``+`` button is left in place as the "add more files" affordance.
+   First-child wrapper of ``stFileChips`` holds the chip flex container;
+   collapsing it lets the ``+`` button hug the dropzone's left edge. */
+[data-testid="stFileChip"] { display: none !important; }
+[data-testid="stFileChips"] > div:first-child { display: none !important; }
 
 /* ---------- Expanders + bordered containers → editorial cards ---------- */
 [data-testid="stExpander"] details,