## Problem
Integration keys (`fugitive`, `neogit`, `gitsigns`, `committia`,
`telescope`)
live at the top level of `vim.g.diffs`, cluttering the config namespace.
## Solution
Move them under `vim.g.diffs.integrations.*`. Old top-level keys still
work but
emit `vim.deprecate` targeting v0.3.2. `compute_filetypes` and
`plugin/diffs.lua`
fall back to legacy keys for pre-`init()` callers.
Also includes `83c17ac` which fixes an invalid hex hash in the combined
diff test
fixture.
## Problem
Regressions #119 and #120 showed the test suite had no coverage of the
decoration provider cache pipeline, no end-to-end pipeline tests from
buffer content to extmarks, and no Neogit-specific integration tests.
## Solution
Adds three new spec files (28 new tests, 316 total):
- `spec/decoration_provider_spec.lua` — indirect cache pipeline tests
via `_test` table: `ensure_cache` population, content fingerprint guard,
`pending_clear` semantics, BufWipeout cleanup
- `spec/integration_spec.lua` — full pipeline: diff buffer → `attach` →
extmarks; verifies `DiffsAdd`/`DiffsDelete` on correct lines, treesitter
captures, multi-hunk coverage
- `spec/neogit_integration_spec.lua` — `neogit_disable_hunk_highlight`
behavior, NeogitStatus/NeogitDiffView attach and cache population,
parser neogit filename patterns
Depends on #133.
Closes#122
