fix(builtins): track uucore quoting-style rename in printf shim

[chaliy]

What changed

The weekly Coreutils Args Drift workflow runs again. It has failed every
scheduled run since 2026-10-05, so bashkit has silently stopped tracking
upstream uutils for two cycles.

The handwritten format_support shim now provides both spellings of two
uucore symbols that upstream renamed, so the vendored format module
compiles whether it is regenerated against the current pin or against
upstream HEAD. No runtime behavior changes.

Separately, the style printf uses to recover a rejected numeric argument
is now named once and enforced by a test, closing a silent-failure path the
drift PR could not have fixed itself.

Why

The drift job re-ports vendored uucore modules against upstream HEAD, then
builds. Upstream renamed QuotingStyle::C_NO_QUOTES to an Escape variant
and extracted locale_aware_shell_escape as a %q shorthand, so the
regenerated code referenced symbols the shim did not have:

error[E0432]: unresolved import `...::format_support::locale_aware_shell_escape`
error[E0599]: no variant or associated item named `Escape` found for enum `QuotingStyle`
error: could not compile `bashkit` (lib) due to 2 previous errors

Both are pure renames. Escape and C_NO_QUOTES both select uucore's
CQuoter with CQuotesEnforce::None, and both are what
--quoting-style=escape resolves to; locale_aware_shell_escape(x) is
locale_aware_escape_name(x, SHELL_ESCAPE) returning String.

The failure is invisible by construction: the job only runs Mondays, and it
dies at Verify build still passes — after regeneration, before the patch
upload — so no PR ever opens and nothing reports the breakage.

Carrying both spellings is deliberate. The pinned generated/format/ still
says C_NO_QUOTES while the regeneration says Escape, and the shim has to
satisfy both at once or the drift run cannot reach its own build step. The
old spelling is dropped once the pin moves past the rename; the condition is
written down in the knowledge entry.

The coupling the drift PR could not repair

printf's numeric_argument_diagnostics recovers a rejected argument by
re-quoting each candidate with the same QuotingStyle the vendored module
used, then prefix-matching the diagnostic. The open-pr job enforces a
generated-only diff, so it can never update printf.rs — a style mismatch
would have dropped printf: <arg>: invalid number silently, and only for
arguments the two styles escape differently. Plain abc escapes to itself
under every style, so printf_invalid_number_stderr could not catch it.

The style is now format_support::DIAGNOSTIC_QUOTING_STYLE, and a test
scans generated/format/argument.rs for the styles it actually names,
failing if any escapes differently.

Before / After

Re-running the workflow's own steps locally against upstream HEAD
781b4991d (pin is 6579cc2), on this branch vs. its parent:

Step	Before	After
port-module format + 11 arg surfaces	regenerates	regenerates
cargo build -p bashkit	E0432 + E0599, exit 101	passes
cargo test --test integration -- spec_tests::bash_spec_tests	never reached	1 passed
cargo test --test integration -- coreutils_differential_tests::	never reached	22 passed

The differential run used a coreutils multicall built from that same
upstream tree, matching how the workflow builds it. That is the last step of
the regenerate job, so the whole job now passes end to end.

Regenerated code confirmed to use the new names:

format/argument.rs:173:  locale_aware_escape_name(OsStr::new(input), QuotingStyle::Escape)
format/spec.rs:354:      let s = locale_aware_shell_escape(args.next_string(*position));

The coupling guard passes in both states — against the pinned tree
(C_NO_QUOTES) and against the regenerated tree (Escape) — which is the
property that makes the upcoming drift PR safe to merge.

No user-visible behavior change: printf reports the raw argument, as bash
does, and the escaped form is only ever a matching key. The new printf test
pins the control-character case against bash 5.2.21:

$ printf '%d' $'a\tb'
bash: printf: a<TAB>b: invalid number

Risk

• Low. Additive shim surface plus one constant; no generated files and no
  resource limits touched. The two upstream changes are renames verified
  against uutils source at both revisions, not semantic changes.
• The dual spelling is transitional cruft by design. If it were dropped too
  early the drift run breaks again — which is why the removal condition is
  recorded in knowledge/runtimes/coreutils-args-port.md rather than left to
  memory.
• This unblocks the drift automation; it does not itself bump the pin. The
  next run opens the regeneration PR for review, as designed.

Checklist

• Tests added or updated
• Backward compatibility considered

https://claude.ai/code/session_0112F7oWpuuyUKiXHbhqRGc1

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