feat: add stdin/pipe support

[PPRAMANIK62]

Summary

• Add support for reading markdown from stdin via pipes (echo "# Hello" | mdt, cat README.md | mdt, mdt -)
• Stdin mode is read-only: editor, file tree, and file finder are disabled with clear status messages
• Navigation, search, help overlay, link picker, and quit all work normally on piped content

Changes

File	What
src/app/mod.rs	stdin_mode field, App::from_stdin() constructor, display_file_path() returns <stdin>
src/main.rs	Stdin detection, eager read before terminal setup, skip bg color detection for pipes, branched init, run_loop takes Option<&Receiver>
src/input/editor.rs	Guard enter_editor() — "Read-only (stdin)"
src/input/normal.rs	Guard toggle_file_tree() — no-op in stdin mode
src/app/file_finder.rs	Guard open_file_finder() — "Not available (stdin)"
src/ui/status_bar.rs	Show line position for stdin content
src/app/tests.rs	8 new tests for stdin mode
website/	Document stdin support in configuration and getting-started docs

Test plan

• cargo test — 300 tests pass (8 new stdin tests, 0 regressions)
• cargo clippy -- -D warnings — clean
• cargo fmt --check — clean
• echo "# Hello World" | cargo run — renders heading
• echo "# Hello\n\n- item 1\n- item 2" | cargo run — renders list
• cargo run -- - with typed input then Ctrl+D — renders stdin
• cargo run (no pipe) — existing behavior unchanged
• i/e in stdin mode — shows "Read-only (stdin)"
• Space+e in stdin mode — does nothing
• ff in stdin mode — shows "Not available (stdin)"
• Scrolling, / search, heading jump, ? help, q quit — all work

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added stdin mode: pipe Markdown into the app for read-only preview (e.g., cat file.md | mdt or mdt -). Editor, file finder, and file-tree toggling are disabled; a stdin pseudo-path is shown.

• Documentation

  • Added docs and examples for reading Markdown from stdin.

• Tests

  • Added tests covering stdin-mode behavior (UI focus, read-only enforcement, navigation, help, quit).

• Chores

  • Updated project/site URLs in docs and metadata.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ba8ab492-2a91-4578-8453-3336d1d05ff7

📥 Commits

Reviewing files that changed from the base of the PR and between 73188a0 and 8128b2a.

📒 Files selected for processing (4)

• Cargo.toml
• README.md
• website/astro.config.ts
• website/src/components/LandingLayout.astro

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📝 Walkthrough

Walkthrough

Adds a piped-stdin read-only mode: main detects piped input, reads content, constructs the app via App::from_stdin(...), and disables editor, file tree, and file finder while rendering the document in preview mode.

Changes

Cohort / File(s)	Summary
App Core src/app/mod.rs, src/app/file_finder.rs	Added stdin_mode: bool and App::from_stdin(...); display_file_path() returns "<stdin>" in stdin mode. open_file_finder() now short-circuits with status "Not available (stdin)" when stdin mode is active.
Input & Interaction src/input/editor.rs, src/input/normal.rs	enter_editor() and toggle_file_tree() short-circuit in stdin mode (set status messages "Read-only (stdin)" / prevent toggling), preventing editor creation and file-tree visibility changes.
Startup & Runtime src/main.rs	Detects piped stdin (or -), reads content (enforces --max-file-size), uses App::from_stdin(...) for piped mode, skips lockfile and watcher, and makes watcher/lockfile teardown conditional; run_loop accepts optional watcher receiver.
UI src/ui/status_bar.rs	Line counter now also renders for stdin mode when rendered_lines non-empty.
Tests src/app/tests.rs	Added tests covering App::from_stdin behavior: stdin initialization, read-only enforcement (editor/file-tree/file-finder), pseudo-path display, navigation/search/help, and quitting.
Docs / Website website/src/content/docs/configuration.mdx, website/src/content/docs/getting-started.mdx	Documented piped-stdin usage and - path, read-only semantics, examples (`echo ...
Metadata / Site Cargo.toml, website/astro.config.ts, website/src/components/LandingLayout.astro, README.md	Updated homepage/site URL references from https://mdtui.pages.dev/... to https://mdt.purbayan.me/....

Sequence Diagram

sequenceDiagram
    participant User
    participant Main as main()
    participant Stdin
    participant App
    participant UI

    User->>Main: invoke mdt with piped input
    Main->>Stdin: detect piped stdin / read content (enforce max size)
    Stdin-->>Main: content string
    Main->>App: App::from_stdin(content, bg_color)
    App->>App: render markdown, rebuild caches, set stdin_mode
    Main->>UI: render read-only preview (no lockfile, no watcher)
    UI-->>User: display document (editor/file-tree/file-finder disabled)

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Poem

🐇 I nibble bytes from pipes at night,

stdin glows, a soft preview light,
No keys to worry, no tree to roam,
Just rendered Markdown, snug as home,
Hop, enjoy the read-only sight! 📜✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: add stdin/pipe support' directly and clearly summarizes the main change—adding stdin/pipe input capability to the application.
Docstring Coverage	✅ Passed	Docstring coverage is 89.47% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/stdin-pipe-support

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