F1 steps 2-6: the Storage App, its viewers, and Maintenance moved in (#3)

The Storage App browses the SD card: folders first with sizes and dates,
three sorts, one item at a time with a clipboard (c, x, v), rename, delete
after counting what's inside, new folder, details. A listing holds 256
entries and says when a folder has more.

FileOps does the card's work for the App and the console alike, one
operation at a time on the storage task in turns of about 150 ms, so Logs
and Captures are still written during a long copy. A copy shows progress,
can be cancelled (what it wrote is taken back) and compares sizes after.
The read-only rules are checked there: the firmware's top-level folders,
/gemini/cache, and files being written (a Track, a Capture, an upload,
today's IRC Logs). A listing reads the folder straight from FatFs: through
the Arduino File, 329 entries took over two seconds.

Viewers by type: text read a screen at a time whatever the file's size
(logs open at the end), a hex dump, a Capture's packets as the LoRa Scanner
lists them, a Track's summary, and an Update File checked as an install
would check it, without writing anything. Tab shows any file as hex or text.

Settings > Storage is gone: usage, Storage Clean-up and Erase are the App's
Maintenance, behind a warning. The Storage Warning points there.

The Clock sets the system time whatever its source, so files are dated
correctly with a GNSS Fix alone (Q137).

Console: cp, mv, mkdir, du, cancel; rm takes folders and follows the rules;
ls shows dates; Debug Builds get `sd fill`.

424 host tests. Checked on the device: docs/milestones/F1.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

lib/files/src/text_pager.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <string>
+#include <vector>
+
+namespace roro::files {
+
+// A text file of any size, shown a screen at a time (F1, Q134): only the part on screen is read,
+// through `read`, about a kilobyte at once. Lines wrap at spaces, `cols` characters wide. Going
+// back a line means finding where the paragraph before started and wrapping it again, so a file
+// reads the same whichever way it was scrolled.
+class TextPager {
+   public:
+    // Reads up to `len` bytes at `offset`; returns how many it got.
+    using ReadAt = std::function<size_t(uint32_t offset, uint8_t* into, size_t len)>;
+
+    TextPager(ReadAt read, uint32_t size, int cols, int rows);
+
+    void toStart() { top_ = 0; }
+    void toEnd();  // the last line at the bottom of the screen
+    void down(int lines = 1);
+    void up(int lines = 1);
+
+    std::vector<std::string> lines();  // what's on screen: tabs as spaces, control characters as dots
+    uint32_t top() const { return top_; }
+    uint32_t size() const { return size_; }
+    bool atEnd();  // the file's last line is on screen
+    int percent() const { return size_ ? static_cast<int>(static_cast<uint64_t>(top_) * 100 / size_) : 0; }
+
+   private:
+    static constexpr size_t kBlock = 1024;       // read at once
+    static constexpr uint32_t kLookBack = 1024;  // how far back a paragraph's start is looked for
+
+    const uint8_t* bytes(uint32_t at, size_t& len);  // what's cached from `at` on
+    int byteAt(uint32_t at);                         // -1 past the end
+    uint32_t nextLine(uint32_t at, std::string* text);  // where the line after the one at `at` starts
+    uint32_t lineBefore(uint32_t at);
+
+    ReadAt read_;
+    uint32_t size_;
+    int cols_, rows_;
+    uint32_t top_ = 0;
+    std::vector<uint8_t> cache_;
+    uint32_t cacheAt_ = 0;
+};
+
+}  // namespace roro::files