* feat(config): add icons table with unicode defaults
* feat(buffer): render icon overlays from config.icons
Problem: status characters ([ ], [x], [!]) and metadata prefixes are
hardcoded literals with no user customization.
Solution: read config.icons in apply_extmarks and apply overlay
extmarks for checkboxes/headers, replace hardcoded recur ↺ with
icons.recur, and prefix due/category virt_text with configurable
icon characters.
* feat(plugin): add PendingTab command and <Plug>(pending-tab)
* docs: add icons config, PendingTab recipes, and demo infrastructure
Problem: icon customization and auto-start workflow are undocumented;
no demo asset exists for the README.
Solution: document pending.Icons in vimdoc with nerd font and ASCII
recipes, add PendingTab to commands and mappings, add open-on-startup
recipe, add demo-init.lua and demo.tape for VHS screenshot generation,
add assets/ directory, add README icons section and demo placeholder.
* ci: format
64b19360b1