fix: pre-release cleanup for v0.2.0 (#102)

## Problem

Three minor issues remain before the v0.2.0 release:

1. Git quotes filenames containing spaces, unicode, or special
characters
   in the fugitive status buffer. `parse_file_line` passed the quotes
   through verbatim, causing file-not-found errors on diff operations.

2. Navigation wrap-around in both conflict and merge modules was silent,
giving no indication when jumping past the last/first item back to the
   beginning/end.

3. `resolved_hunks` and `(resolved)` virtual text in the merge module
persisted across buffer re-reads, showing stale markers for hunks that
   were no longer resolved.

## Solution

1. Add an `unquote()` helper to fugitive.lua that strips surrounding
   quotes and unescapes `\\`, `\"`, `\n`, `\t`, and octal `\NNN`
   sequences. Applied to both return paths in `parse_file_line`.

2. Add `vim.notify` before the wrap-around jump in all four navigation
   functions (`goto_next`/`goto_prev` in conflict.lua and merge.lua).

3. Clear `resolved_hunks[bufnr]` and the merge namespace at the top of
   `setup_keymaps` so each buffer init starts fresh.

Closes #66

doc/diffs.nvim.txt

@@ -75,6 +75,12 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
           algorithm = 'default',
           max_lines = 500,
         },
+        priorities = {
+          clear = 198,
+          syntax = 199,
+          line_bg = 200,
+          char_bg = 201,
+        },
         overrides = {},
       },
       fugitive = {
@@ -161,6 +167,10 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              Character-level (intra-line) diff highlighting.
                              See |diffs.IntraConfig| for fields.
 
+        {priorities}         (table, default: see below)
+                             Extmark priority values.
+                             See |diffs.PrioritiesConfig| for fields.
+
         {overrides}          (table, default: {})
                              Map of highlight group names to highlight
                              definitions (see |nvim_set_hl()|). Applied
@@ -182,6 +192,28 @@ Configuration is done via `vim.g.diffs`. Set this before the plugin loads:
                              direction. Lines are read with early exit —
                              cost scales with this value, not file size.
 
+                                                   *diffs.PrioritiesConfig*
+    Priorities config fields: ~
+        {clear}              (integer, default: 198)
+                             Priority for `DiffsClear` extmarks that reset
+                             underlying diff foreground colors. Must be
+                             below {syntax}.
+
+        {syntax}             (integer, default: 199)
+                             Priority for treesitter and vim syntax extmarks.
+                             Must be below {line_bg} so that colorscheme
+                             backgrounds on syntax groups do not obscure
+                             line-level diff backgrounds.
+
+        {line_bg}            (integer, default: 200)
+                             Priority for `DiffsAdd`/`DiffsDelete` line
+                             background extmarks. Must be below {char_bg}.
+
+        {char_bg}            (integer, default: 201)
+                             Priority for `DiffsAddText`/`DiffsDeleteText`
+                             character-level background extmarks. Highest
+                             priority so changed characters stand out.
+
                                                     *diffs.TreesitterConfig*
     Treesitter config fields: ~
         {enabled}            (boolean, default: true)
@@ -418,6 +450,7 @@ Configuration: ~
         disable_diagnostics = true,
         show_virtual_text = true,
         show_actions = false,
+        priority = 200,
         keymaps = {
           ours = 'doo',
           theirs = 'dot',
@@ -471,6 +504,11 @@ Configuration: ~
                              `DiffsConflictActions` highlight group.
                              Only keymaps that are not `false` appear.
 
+        {priority}           (integer, default: 200)
+                             Extmark priority for conflict region
+                             backgrounds and markers. Adjust if other
+                             plugins use the same priority range.
+
         {keymaps}            (table, default: see above)
                              Buffer-local keymaps for conflict resolution
                              and navigation. Each value accepts a string
@@ -566,12 +604,13 @@ Summary / commit detail views: ~
    - Code is parsed with |vim.treesitter.get_string_parser()|
    - If no treesitter parser and `vim.enabled`: vim syntax fallback via
      scratch buffer and |synID()|
-   - `Normal` extmarks at priority 198 clear underlying diff foreground
-   - Background extmarks (`DiffsAdd`/`DiffsDelete`) at priority 199
-   - Syntax highlights are applied as extmarks at priority 200
+   - `DiffsClear` extmarks at priority 198 clear underlying diff foreground
+   - Syntax highlights are applied as extmarks at priority 199
+   - Background extmarks (`DiffsAdd`/`DiffsDelete`) at priority 200
    - Character-level diff extmarks (`DiffsAddText`/`DiffsDeleteText`) at
      priority 201 overlay changed characters with an intense background
    - Conceal extmarks hide diff prefixes when `hide_prefix` is enabled
+   - All priorities are configurable via |diffs.PrioritiesConfig|
 4. Re-highlighting occurs on `TextChanged` (debounced) and `Syntax` events
 
 Diff mode views: ~
@@ -586,15 +625,10 @@ KNOWN LIMITATIONS                                       *diffs-limitations*
 
 Incomplete Syntax Context ~
                                                       *diffs-syntax-context*
-Treesitter parses each diff hunk in isolation. To provide surrounding code
-context, diffs.nvim reads lines from disk before and after each hunk
-(see |diffs.ContextConfig|, enabled by default). This resolves most boundary
-issues where incomplete constructs (e.g., a function definition at the edge
-of a hunk with no body) would confuse the parser.
-
-Set `highlights.context.enabled = false` to disable context padding. In rare
-cases, context padding may not help if the relevant surrounding code is very
-far from the hunk boundaries.
+Treesitter parses each diff hunk in isolation. Context lines within the hunk
+(lines with a ` ` prefix) provide syntactic context for the parser. In rare
+cases, hunks that start or end mid-expression may produce imperfect highlights
+due to treesitter error recovery.
 
 Syntax Highlighting Flash ~
                                                              *diffs-flash*