chore: fix CI branch trigger and add project READMEs

* ci.yml: trigger on pushes/PRs to master instead of main. The repo's
  default branch is master, so the previous config never fired and CI
  silently passed on every commit.

* Add README.md (English) and README-zh.md (Chinese), the bilingual
  project documentation referenced by AGENTS.md.

README.md

@@ -0,0 +1,104 @@
+# logViewer
+
+**[中文文档](README-zh.md)**
+
+A high-performance terminal log file viewer built in Rust, designed to handle multi-gigabyte files with minimal memory overhead.
+
+Uses memory-mapped I/O with a sparse line index and progressive background loading to open files instantly — even 5GB+ logs scroll smoothly from the first keystroke.
+
+## Features
+
+- **Instant file open** — mmap-backed reader with background progressive indexing; start scrolling before indexing finishes
+- **Handles huge files** — sparse line index (1 entry per 256 lines) keeps memory usage at ~8MB even for 5GB files
+- **Live file tracking** — watches for appends, truncations, and log rotation via `notify`
+- **JSON log support** — NDJSON parsing with BOM handling, duplicate key detection, and toggleable pretty-printing
+- **Unicode-aware wrapping** — correct line wrapping for CJK, emoji, and tabs
+- **Persistent index cache** — line indexes saved to disk with xxh3 content hashing; re-opens are near-instant
+- **Vim-like keybindings** — familiar navigation for terminal users
+- **Customizable colors** — per-log-level colors via TOML config, adjustable from within the TUI
+
+## Quick Start
+
+```bash
+# Build and run
+cargo run -p log-viewer-tui -- path/to/logfile.log
+
+# Or build first
+cargo build --release -p log-viewer-tui
+./target/release/log-viewer-tui path/to/logfile.log
+```
+
+Requires Rust 1.92+ (see `rust-toolchain.toml`).
+
+## Keybindings
+
+| Key | Action |
+|-----|--------|
+| `j` / `↓` | Scroll down one line |
+| `k` / `↑` | Scroll up one line |
+| `Ctrl+d` | Scroll down half page |
+| `Ctrl+u` | Scroll up half page |
+| `Ctrl+f` / `PgDn` | Scroll down full page |
+| `Ctrl+b` / `PgUp` | Scroll up full page |
+| `G` / `End` | Jump to end of file |
+| `gg` / `Home` | Jump to start of file |
+| `Tab` | Toggle JSON pretty-printing |
+| `S` | Open color settings |
+| `q` / `Esc` | Quit |
+
+Settings panel: use `j`/`k` to select a log level, `←`/`→` to cycle colors, `Enter` to save, `Esc` to cancel.
+
+## Workspace Structure
+
+```
+crates/core  — Shared library: I/O, parsing, types, config, file watching
+crates/tui   — Terminal UI (ratatui + crossterm)
+crates/gui   — GUI (egui + eframe) — placeholder, not yet functional
+crates/bench — mmap vs pread benchmark harness
+```
+
+## Development
+
+```bash
+# Check, test, lint
+cargo check --workspace
+cargo test --workspace
+cargo fmt --check --all
+cargo clippy --workspace -- -D warnings
+
+# Run benchmarks (generates ~5GB test file on first run)
+cargo run -p log-viewer-bench
+cargo run -p log-viewer-bench -- --quick --suites startup,render --output results.md
+
+# Test a single crate
+cargo test -p log-viewer-core
+cargo test -p log-viewer-tui
+```
+
+### CI
+
+The CI gate runs on ubuntu-latest and windows-latest:
+1. `cargo fmt --check --all`
+2. `cargo check --workspace`
+3. `cargo test --workspace`
+4. `cargo clippy --workspace -- -D warnings`
+
+No custom rustfmt or clippy config — uses toolchain defaults.
+
+## Architecture
+
+The core library (`log-viewer-core`) owns all I/O, parsing, and data types. Key design decisions:
+
+- **Sparse line index** — samples every 256 lines using memchr SIMD acceleration. A 1M-line file produces a ~32KB index instead of ~8MB.
+- **Progressive loading** — `ProgressiveFileReader` starts with a quick head+tail sample for instant line estimates, then builds the full index in a background thread via crossbeam-channel.
+- **mmap with TOCTOU mitigation** — post-mmap stat check to detect file changes. `read_cache` module exists as a future pread-based alternative to eliminate SIGBUS risk entirely.
+- **Persistent cache** — line indexes are serialized to disk with xxh3 content hashing for invalidation. Atomic writes via temp files.
+- **Visual height index** — prefix-sum over wrapped-line heights, enabling O(log n) scroll-to-line mapping for long wrapped lines.
+
+Planned but not yet built: filtering, bookmarks, sessions, search engine (stub modules exist).
+
+## Benchmarks
+
+Custom harness comparing mmap vs pread backends across 7 suites (startup, render, jump, memory, growth, rotation, concurrent). Uses wall-clock timing with `/proc/self/` RSS and page fault metrics. Results are written as markdown tables to `benchmark-report.md`.
+
+The benchmark binary includes ~75 unit tests for the reader backends and metrics collection.