feat: Process ui (#2)

* Add Phase 2 processes table design spec

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Update spec: all user-facing text in English

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Add Phase 2 processes table implementation plan

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(platform): add process_list() to SwapBackend, implement in LinuxBackend

* feat(actions): add SortColumn, SortDir, navigation and filter actions

* feat(app): add processes sort/filter/navigation state and reducer

* feat(collector): parallel smaps collection via processes_active flag

* feat(main): context-aware keyboard routing and processes_active wiring

* feat(ui): wire processes tab, context-aware statusbar, user docs

* refactor(processes): build_layout returns Rc<[Rect]> with indexed footer slot

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(processes): add render_footer with key_span/desc_span context-aware hints

* refactor(statusbar): global-only keybindings; context hints moved to processes panel

* fix(review): address critical and minor code review issues

- Use spawn_blocking for smaps I/O (was blocking async executor)
- Remove duplicate process_swap from trait and all backends
- Add Copy to SortColumn/SortDir; drop redundant .clone() calls
- Add next_sort_column unit tests in main.rs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs: add statusbar refactor implementation plan

* docs: add processes screen performance fix design spec

Replace smaps-based per-process swap collection with lightweight /proc
reader using /proc/{pid}/status + /proc/{pid}/stat for 90%+ CPU reduction.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs: add processes performance fix implementation plan

8-task TDD plan: ProcReader module with /proc/{pid}/status + stat
parsing, LinuxBackend delegation, Collector simplification.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(proc_reader): add parse_status with tests

Introduces src/platform/proc_reader.rs with StatusInfo struct,
parse_status() and parse_kb_value() helpers, and 4 unit tests
covering normal fields, missing name, kernel threads, and zero swap.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat(proc_reader): add parse_stat_cpu_ticks with tests

Parse /proc/{pid}/stat to extract utime+stime CPU ticks. Uses rfind(')')
to correctly handle comm fields containing spaces or nested parentheses.

* feat(proc_reader): add ProcReader struct with collect() method

Adds ProcReader with new(), collect(), and resolve_user() that reads
/proc/{pid}/status + /proc/{pid}/stat sequentially — replacing the
per-process spawn_blocking approach for CPU-efficient process listing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* refactor(linux): delegate process_list() to ProcReader

Wire ProcReader into LinuxBackend: add proc_reader field, remove sysinfo-based process collection, and replace process_list() body with proc_reader.collect(). Drop unused Users field and sysinfo::Users import. Suppress dead_code on is_kernel_thread (removal is Task 6).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* refactor(collector): remove smaps/spawn_blocking, use direct process_list()

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore(linux): remove duplicated is_kernel_thread (now in proc_reader)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test(proc_reader): add is_kernel_thread tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ricsdeol

docs/processes-screen.md

@@ -0,0 +1,40 @@
+# Processes Screen
+
+The Processes screen (tab `2`) shows all running user-space processes with their
+memory and CPU usage. Press `2` or `Tab` to reach it.
+
+## Columns
+
+| Column | Description |
+|--------|-------------|
+| PID    | Process ID |
+| Name   | Executable name |
+| User   | Owner of the process |
+| RSS    | Resident memory in use (RAM) |
+| Swap   | Swap space in use (Linux only) |
+| CPU%   | Current CPU usage |
+
+The active sort column is marked with `▾` (descending) or `▲` (ascending).
+
+## Navigation
+
+| Key | Action |
+|-----|--------|
+| `j` / `↓` | Move selection down |
+| `k` / `↑` | Move selection up |
+| `s` | Cycle sort column (Swap → CPU% → RSS → PID → Name → Swap) |
+| `/` | Open filter input |
+| `Enter` | Open process detail *(Phase 3)* |
+
+## Filtering
+
+Press `/` to open the filter bar. Type to narrow the list by process name.
+Press `Enter` or `Esc` to close the filter bar — the filter text stays active
+until you clear it with `Backspace`.
+
+## Platform notes
+
+**Linux:** All columns available. Swap per process is read from `/proc/PID/smaps`.
+
+**macOS / other:** The Swap column shows `—`. Swap per process is not available
+without private kernel APIs.