Revert the scrolling calendar: back to moving the two-week window with [ and ]

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

SPECS.md

@@ -64,7 +64,7 @@ Notes:
   - Global speed / pause state in the status bar. Pause/resume and delete a SABnzbd job.
 - **Status bar / help:** the bottom bar lists the keys that work in the current view or panel; the top right shows the connection state of each service; `?` opens the full key reference.
 - **Posters:** the detail panes show the poster at the top right; the head (title, facts, path) and the plot are one text that flows along the poster's left side and continues at full width below it (text is wrapped by arr-tui itself, with a narrower width for the first lines); on panes too small for the poster, the text simply uses the full width. The poster is drawn with block characters in 24-bit colors: every cell shows several pixels in the best two-color split (`quadrant`: 2×2 pixels, glyphs from the Block Elements range every font has; `sextant`: 2×3 pixels, sharper, glyphs from Symbols for Legacy Computing). `ui.cover_style` is `auto` (default: sextant on kitty, WezTerm, foot, Ghostty, quadrant elsewhere), `quadrant` or `sextant`. JPEG/PNG only, decoded and downscaled in the process, so no terminal graphics protocol is needed. Library items fetch `/MediaCover/<id>/poster-250.jpg` from their Radarr/Sonarr instance with the API key; search results fall back to the provider's `remoteUrl` (fetched without credentials). Posters are cached in memory, failed downloads are not retried for two minutes, and the poster shrinks or disappears when the pane is too short. `ui.covers: false` disables it.
-- **Calendar view (F5):** one scrolling list of the library's movie releases and airing episodes, grouped by day. It starts with 7 days back and 28 ahead, today's header at the top, and loads another 28 days whenever the selection comes within 6 rows of either end (or ↓/↑ is pressed at an end), up to about 180 days back and 400 ahead; the selection and scroll position stay put when days are added above. `t` returns to today (resetting the list if it was left), `u` includes unmonitored items, `r` reloads. Radarr `GET /calendar` supplies the cinema, digital and physical release dates (taken as written: midnight UTC means that calendar day) and Sonarr `GET /calendar?includeSeries=true` the episodes with their air time (shown in local time). A movie appears once per release date. Each entry shows type, title, episode or release kind and status (downloaded / missing / upcoming); the detail pane shows poster and plot; `Enter`/`i` starts the release search and `s` an automatic search.
+- **Calendar view (F5):** a two-week window (starting today, moved a week at a time with `[`/`]`, `t` returns to today) with the library's movie releases and airing episodes, grouped by day. Radarr `GET /calendar` supplies the cinema, digital and physical release dates (taken as written: midnight UTC means that calendar day) and Sonarr `GET /calendar?includeSeries=true` the episodes with their air time (shown in local time). Unmonitored items are included with `u`. A movie appears once per release date in the window. Each entry shows type, title, episode or release kind and status (downloaded / missing / upcoming); the detail pane shows poster and plot; `Enter`/`i` starts the release search and `s` an automatic search.
 - **Download notifications:** a background poller (independent of the visible view) reads SABnzbd's history every 15 s and announces downloads that reach `Completed` or `Failed` as a popup and log entry; the first poll only records the current state. `ui.notify_downloads` (default true) and `ui.bell` (default false, rings the terminal bell) control it. Connection errors are not reported here, the indicators and the log already do that.
 - **Notifications and log (F5):** feedback about actions (added, deleted, grabbed, failures) appears as popups in the bottom right that fade away (errors stay longer). Everything is also kept in the Log view; only connection changes of the background polling are logged, not every failed poll.
 
@@ -115,7 +115,7 @@ Keybindings (the status bar shows the ones that apply to the current view):
 | `i` | Movies, Series, Library: interactive release search (series: seasons and episodes) |
 | `F` | Library and release list: filter by properties (quality, codec, HDR/DV, audio, language) |
 | `f` | Library: cycle the status filter; release list: hide rejected releases |
-| `t` `u` | Calendar: back to today, include unmonitored (scroll for more days) |
+| `[` `]` `t` `u` | Calendar: week back / forward, today, include unmonitored |
 | `d` | Library: remove the item from the library (asks first) |
 | `t` | Library, episodes: toggle monitored; Downloads history: retry a failed download |
 | `s` | Library, episodes: automatic search; release list: cycle sort (best / size / age) |