- Correct push_path/push_back function name mismatch
- Fix non-compiling call sites in the &Path example so the snippet
  type-checks against the stated signature
- Add missing `move` and trailing `;` to tokio::task::spawn examples
  so they compile
- Rename "Cloning an atomic counter" section to "Cloning `Arc` and `Rc`"
  since Arc/Rc are reference counters, not atomic counters
- Fix missing semicolon in an assert_eq! example
- Grammar fixes ("could easily be refactored", "Explicitly marking
  the cloned type aids", "as more pull requests are reviewed")

Adapted from KSXGitHub/parallel-disk-usage's CONTRIBUTING.md, with
pacquet-specific changes:

- No version-release exception in the commit message convention
- Setup and automated-check sections rewritten around `just init`,
  `just install`, and `just ready` instead of `test.sh`
- Dropped the squashfs/fuse external-dependency section (not relevant
  to pacquet); kept the registry-mock note instead
- Examples reworked to use pacquet types (manifests, store, etc.)
- Cross-links between CONTRIBUTING.md and CODE_STYLE_GUIDE.md so the
  two documents are discovered together

AGENTS.md instructs AI agents to follow both guides.

…DE.md

Per option A of the contributing/style split discussion: keep
CONTRIBUTING.md focused on process (commit message format, writing
style, setup, automated checks), and have CODE_STYLE_GUIDE.md own
every code-level convention.

Moved into CODE_STYLE_GUIDE.md (under the existing `## Guides`
section, in thematic order):

- Module Organization
- Import Organization
- Derive Macro Ordering
- Generic Parameter Naming
- Variable and Closure Parameter Naming (with the single-letter rules)
- Trait Bounds
- Pattern Matching
- Using `pipe-trait` (with when-to-use and when-not-to-use)
- Error Handling
- Conditional Test Skipping (`#[cfg]` vs `#[cfg_attr(..., ignore)]`)
- Unit test file layout (was the top-level `## Unit Tests` section)

The intra-doc link from "Where the external file sits" to
"Module Organization" still resolves because both sections now live
in the same file.

Updated `AGENTS.md`'s descriptions for both guides to reflect the new
split. Per the review thread on this PR, no other prose in
`AGENTS.md` was rewritten for writing-style conformance; that is
deferred to the maintainer.

The pair was meant to contrast the closure parameter name (`entry`
vs. `x`), but using `.filter_map` on the good side and `.filter` on
the bad side muddled that with a method-choice difference. The
mismatch was carried over from the upstream parallel-disk-usage
guide. Use `.filter` on both sides so the example isolates the rule
under discussion.

The text says "to pass a reference mid-chain", but the example was
a single `path_buf.pipe_as_ref(Path::exists)` call with no chain at
all. Replaced with a four-step chain that has methods before and
after `pipe_as_ref`, so the rule's wording matches the demonstration.

Audited every other pipe example in the section: each one is either
already part of a chain (dependencies, into_iter, summarize, etc.)
or is intentionally chain-free in the "When NOT to use pipe"
section, so no other rectification was needed.

Addresses KSXGitHub review on PR #255.

Replace "Install the registry-mock dependencies" with "Install the
test dependencies". The previous wording named an internal component
(registry-mock) and would drift if `just install` ever did more or
different work. The new wording defers to `just install` as the
source of truth for what gets installed.

Per KSXGitHub review on PR #255.

Per @zkochan review on PR #255: reduce the number of alternatives
listed for index variables. Keep `index` and `*_index` (such as
`row_index`); drop `idx`.

Applied to both places where the triple appeared: the "Conventional
single-letter names" bullet and the "Index variables" rule, so the
two stay consistent.