feat: add Obsidian-style graph visualization

Implement force-directed graph view for visualizing note connections:

- Add graph data model parsing [[wiki-style links]]
- Implement Fruchterman-Reingold layout algorithm
- Create character-based canvas renderer with highlights
- Add interactive filtering by tag/folder
- Support navigation (h/j/k/l), zoom (+/-), and node selection
- New commands: :IdeaGraph, :IdeaGraphFilter

New files:
- lua/ideaDrop/ui/graph/{init,types,data,layout,renderer}.lua

Updated documentation in README.md, CHANGELOG.md, and llms.txt

lua/ideaDrop/core/config.lua

@@ -4,21 +4,34 @@
 ---@field options IdeaDropOptions
 ---@field setup fun(user_opts: IdeaDropOptions|nil): nil
 
+---@class GraphOptions
+---@field animate boolean Whether to animate layout (default: false)
+---@field show_orphans boolean Whether to show orphan nodes (default: true)
+---@field show_labels boolean Whether to show node labels by default (default: true)
+---@field node_colors table<string, string>|nil Custom colors for folders/tags
+
 ---@class IdeaDropOptions
 ---@field idea_dir string Directory where idea files will be stored
+---@field graph GraphOptions|nil Graph visualization options
 
 local M = {}
 
 ---Default configuration options
 M.options = {
-  idea_dir = vim.fn.stdpath("data") .. "/ideaDrop"  -- default path
+	idea_dir = vim.fn.stdpath("data") .. "/ideaDrop", -- default path
+	graph = {
+		animate = false, -- Set to true for animated layout
+		show_orphans = true, -- Show nodes with no connections
+		show_labels = true, -- Show node labels by default
+		node_colors = nil, -- Custom node colors by folder/tag
+	},
 }
 
 ---Setup function to merge user options with defaults
 ---@param user_opts IdeaDropOptions|nil User configuration options
 ---@return nil
 function M.setup(user_opts)
-  M.options = vim.tbl_deep_extend("force", M.options, user_opts or {})
+	M.options = vim.tbl_deep_extend("force", M.options, user_opts or {})
 end
 
 return M