ObsidianTags matches not only `tags` key in frontmatter

### 🐛 Describe the bug

With the following frontmatter:

```yaml
---
aliases:
- Index
tags:
- index
---
```

`:ObsidianTags index` returns two results instead one.

Config

```lua
local obsidian = require('obsidian')

---@diagnostic disable-next-line: missing-fields
obsidian.setup
{
workspaces = {
{
name = "personal",
path = "~/cloud/wiki",
},
},
completion = {
nvim_cmp = true,
min_chars = 0,
},
mappings = {
[""] = {
action = function()
return "ObsidianSearch"
end,
opts = { buffer = true, expr = true },
},
[""] = {
action = function()
return obsidian.util.smart_action()
end,
opts = { buffer = true, expr = true },
},
},

new_notes_location = "notes_subdir",

---@param title string|?
---@return string
note_id_func = function(title)
return os.date("%Y%m%d%H%M%S")
end,

---@param spec { id: string, dir: obsidian.Path, title: string|? }
---@return string|obsidian.Path The full path to the new note.
note_path_func = function(spec)
-- This is equivalent to the default behavior.
local path = spec.dir / tostring(spec.id)
return path:with_suffix(".md")
end,

-- Optional, customize how wiki links are formatted. You can set this to one of:
-- * "use_alias_only", e.g. '[[Foo Bar]]'
-- * "prepend_note_id", e.g. '[[foo-bar|Foo Bar]]'
-- * "prepend_note_path", e.g. '[[foo-bar.md|Foo Bar]]'
-- * "use_path_only", e.g. '[[foo-bar.md]]'
-- Or you can set it to a function that takes a table of options and returns a string, like this:
wiki_link_func = function(opts)
return require("obsidian.util").wiki_link_id_prefix(opts)
end,

-- Optional, customize how markdown links are formatted.
markdown_link_func = function(opts)
return require("obsidian.util").markdown_link(opts)
end,

-- Either 'wiki' or 'markdown'.
preferred_link_style = "wiki",

-- Optional, boolean or a function that takes a filename and returns a boolean.
-- `true` indicates that you don't want obsidian.nvim to manage frontmatter.
disable_frontmatter = false,

-- Optional, alternatively you can customize the frontmatter data.
---@return table
note_frontmatter_func = function(note)
-- Add the title of the note as an alias.
if note.title then
note:add_alias(note.title)
end

local out = { aliases = note.aliases, tags = note.tags }

-- `note.metadata` contains any manually added fields in the frontmatter.
-- So here we just make sure those fields are kept in the frontmatter.
if note.metadata ~= nil and not vim.tbl_isempty(note.metadata) then
for k, v in pairs(note.metadata) do
out[k] = v
end
end

return out
end,

-- templates = {
-- folder = "templates",
-- date_format = "%Y-%m-%d",
-- time_format = "%H:%M",
-- substitutions = {},
-- },

-- Optional, by default when you use `:ObsidianFollowLink` on a link to an external
-- URL it will be ignored but you can customize this behavior here.
---@param url string
follow_url_func = function(url)
vim.ui.open(url) -- need Neovim 0.10.0+
end,

-- Optional, by default when you use `:ObsidianFollowLink` on a link to an image
-- file it will be ignored but you can customize this behavior here.
---@param img string
follow_img_func = function(img)
vim.fn.jobstart({ "xdg-open", img }) -- linux
end,

-- Optional, set to true if you use the Obsidian Advanced URI plugin.
-- https://github.com/Vinzent03/obsidian-advanced-uri
use_advanced_uri = false,

-- Optional, set to true to force ':ObsidianOpen' to bring the app to the foreground.
open_app_foreground = false,

picker = {
-- Set your preferred picker. Can be one of 'telescope.nvim', 'fzf-lua', or 'mini.pick'.
name = "telescope.nvim",
-- Optional, configure key mappings for the picker. These are the defaults.
-- Not all pickers support all mappings.
note_mappings = {
-- Create a new note from your query.
new = "",
-- Insert a link to the selected note.
insert_link = "",
},
tag_mappings = {
-- Add tag(s) to current note.
tag_note = "",
-- Insert a tag at the current location.
insert_tag = "",
},
},

-- Optional, sort search results by "path", "modified", "accessed", or "created".
-- The recommend value is "modified" and `true` for `sort_reversed`, which means, for example,
-- that `:ObsidianQuickSwitch` will show the notes sorted by latest modified time
sort_by = "modified",
sort_reversed = true,

-- Set the maximum number of lines to read from notes on disk when performing certain searches.
search_max_lines = 1000,

-- Optional, determines how certain commands open notes. The valid options are:
-- 1. "current" (the default) - to always open in the current window
-- 2. "vsplit" - to open in a vertical split if there's not already a vertical split
-- 3. "hsplit" - to open in a horizontal split if there's not already a horizontal split
open_notes_in = "current",

-- Optional, define your own callbacks to further customize behavior.
callbacks = {
-- Runs at the end of `require("obsidian").setup()`.
---@param client obsidian.Client
post_setup = function(client) end,

-- Runs anytime you enter the buffer for a note.
---@param client obsidian.Client
---@param note obsidian.Note
enter_note = function(client, note)

end,

-- Runs anytime you leave the buffer for a note.
---@param client obsidian.Client
---@param note obsidian.Note
leave_note = function(client, note) end,

-- Runs right before writing the buffer for a note.
---@param client obsidian.Client
---@param note obsidian.Note
pre_write_note = function(client, note) end,

-- Runs anytime the workspace is set/changed.
---@param client obsidian.Client
---@param workspace obsidian.Workspace
post_set_workspace = function(client, workspace) end,
},

-- Optional, configure additional syntax highlighting / extmarks.
-- This requires you have `conceallevel` set to 1 or 2. See `:help conceallevel` for more details.
ui = {
enable = true, -- set to false to disable all additional syntax features
update_debounce = 50, -- update delay after a text change (in milliseconds)
max_file_length = 5000, -- disable UI features for files with more than this many lines
-- Define how various check-boxes are displayed
checkboxes = {
-- NOTE: the 'char' value has to be a single character, and the highlight groups are defined below.
[" "] = { char = "󰄱", hl_group = "@markup.list.markdown" },
["x"] = { char = "", hl_group = "@markup.list.markdown" },
},
-- Use bullet marks for non-checkbox lists.
bullets = { char = "-", hl_group = "@markup.list.markdown" },
external_link_icon = { char = "", hl_group = "markdownUrlTitle" },
-- Replace the above with this if you don't have a patched font:
-- external_link_icon = { char = "", hl_group = "ObsidianExtLinkIcon" },
reference_text = { hl_group = "@text" },
highlight_text = { hl_group = "Error" },
tags = { hl_group = "@tag" },
block_ids = { hl_group = "Error" },
hl_groups = {
},
},

-- Specify how to handle attachments.
attachments = {
-- The default folder to place images in via `:ObsidianPasteImg`.
-- If this is a relative path it will be interpreted as relative to the vault root.
-- You can always override this per image by passing a full path to the command instead of just a filename.
img_folder = "assets/imgs", -- This is the default

-- Optional, customize the default name or prefix when pasting images via `:ObsidianPasteImg`.
---@return string
img_name_func = function()
-- Prefix image names with timestamp.
return string.format("%s-", os.time())
end,

-- A function that determines the text to insert in the note when pasting an image.
-- It takes two arguments, the `obsidian.Client` and an `obsidian.Path` to the image file.
-- This is the default implementation.
---@param client obsidian.Client
---@param path obsidian.Path the absolute path to the image file
---@return string
img_text_func = function(client, path)
path = client:vault_relative_path(path) or path
return string.format("", path.name, path)
end,
},
}
```

### Environment

```
NVIM v0.11.0-dev
Build type: RelWithDebInfo
LuaJIT 2.1.1703358377
Run "nvim -V1 -v" for more info

Obsidian.nvim v3.9.0 (ae1f76a75c7ce36866e1d9342a8f6f5b9c2caf9b)
Status:
• buffer directory: nil
• working directory: /home/beavis
Workspaces:
✓ active workspace: Workspace(name='personal', path='/home/beavis/cloud/wiki', root='/home/beavis/cloud/wiki')
Dependencies:
✓ plenary.nvim: 2d9b06177a975543726ce5c73fca176cedbffe9d
✓ nvim-cmp: ae644feb7b67bf1ce4260c231d1d4300b19c6f30
✓ telescope.nvim: eae0d8fbde590b0eaa2f9481948cd6fd7dd21656
Integrations:
✓ picker: TelescopePicker()
✓ completion: enabled (nvim-cmp) ✗ refs, ✗ tags, ✗ new
all sources:
• nvim_lsp
• nvim_lua
• tags
• async_path
• zsh
• luasnip
• buffer
Tools:
✓ rg: ripgrep 14.1.0
Environment:
• operating system: Linux
Config:
• notes_subdir: nil%
```

Start by reproducing the issue with the supplied YAML frontmatter and the :ObsidianTags index command. Trace how frontmatter fields are read and how tag matches are collected, focusing on why aliases produce an extra result. Done means the command returns only the note whose tags key contains index, with relevant regression coverage if the project has an existing test location.

Written by the indexing model from the issue text.