fix(declare): bash declaration engine, locals, attributes and set options (105 BashBox cases) - #2597

Replace the string-splitting arithmetic evaluator with a tokenizer and a
precedence-climbing parser that follows bash's expr.c grammar (comma,
assignment operators, ternary, short-circuit with noeval, right-assoc
`**`, base#digits up to 64, pre/post increment on elements).

Errors now behave as in bash: `$((...))` errors print the bash message
and abort the rest of the current line (new ControlFlow::Abort /
Error::LineAbort); `((...))` and `let` return status 1. The body of a
`((...))` command is read raw so `<<=`/`>>` are not lexed as redirects.

Unskips the bashbox-arithmetic-array cases and
bashbox_declare_a_subshell_ends_with_status_1.

declare/typeset/local/export/readonly now run through one engine
(interpreter/declare.rs) with bash's option sets, error messages and
declare -p output (quoting, assoc arrays in bash hash order).

Locals use shallow binding saved in the call frame: nested functions,
unset of a caller's local, declare -g past a local and local -n follow
bash. Compound operands stay one CompoundAssignment word part, so keyed
elements with quotes or backticks lex as one element and analysis walks
substitutions inside them. Readonly assignment and circular namerefs
abandon the line as in bash.

Unskips 60 bashbox declare/attributes/local-scope/read-names cases.

A scalar is element 0 of an array for ${x[@]}, ${#x[@]}, ${!x[@]},
${x[0]} and arithmetic element writes. Associative arrays expand in
bash's hash order. [[ -v ]] was missing and is now implemented.
${!ref} resolves a nameref chain, a nameref for-loop variable is
re-pointed per word, and builtin assignment through a circular nameref
fails the command. read takes options only before names, stops at an
invalid name, validates -a names and supports -N.

Unskips 15 bashbox declare/local-scope/read-names cases.

set knows every set -o option and letter, validates before changing
anything, lets each o in a cluster take the next argument and lists
options for a trailing -o; shopt -o/-po operate on them. $- uses bash's
letter order and defaults (hBc). BASH_SUBSHELL counts subshells, command
and process substitutions. ( ), [[ ]] and (( )) set PIPESTATUS. The
exported environment is snapshotted with subshell state, so (E=2) no
longer leaks. local LINENO is an ordinary variable and cd with HOME
unset fails.

Unskips 12 bashbox attributes/local-scope/shell-variables cases; the
remaining declare skips name their reason (printf -v, ANSI-C bytes).

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# Conflicts:
#	THIRD_PARTY_LICENSES/README.md
#	crates/bashkit/src/builtins/read.rs
#	crates/bashkit/src/builtins/vars.rs
#	crates/bashkit/src/interpreter/mod.rs
#	crates/bashkit/src/parser/lexer.rs
#	crates/bashkit/tests/spec_cases/bash/bashbox-arithmetic-array.test.sh
#	crates/bashkit/tests/spec_cases/bash/bashbox-attributes.test.sh
#	crates/bashkit/tests/spec_cases/bash/bashbox-declare.test.sh
#	crates/bashkit/tests/spec_cases/bash/bashbox-local-scope.test.sh
#	crates/bashkit/tests/spec_cases/bash/bashbox-read-names.test.sh
#	crates/bashkit/tests/spec_cases/bash/bashbox-shell-variables.test.sh
#	knowledge/log.md

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# Conflicts:
#	crates/bashkit/src/interpreter/mod.rs
#	crates/bashkit/tests/integration/blackbox_security_tests.rs
#	knowledge/log.md

Shared by a=(...), a+=(...), declare -a, typeset -a and local -a.
Mixed quoted words like "x"{1,2} expand; keyed assoc values stay
literal; [k]=v{1,2} lexes as one word.

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# Conflicts:
#	crates/bashkit/src/interpreter/mod.rs
#	knowledge/log.md

…-eafupr-bb-vars

A function call is the recursion path. Dispatching it from the same
future as the builtin and PATH-search arms put that whole frame on the
stack at every call level, so 16 nested calls overflowed a 2 MiB stack
in debug builds. Functions now get their own small future, and prefix
assignments are boxed. Debug CLI now reaches the depth limit with
1.75 MiB of stack (main needed more than 1.94 MiB).

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# Conflicts:
#	crates/bashkit/src/interpreter/mod.rs
#	knowledge/log.md

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# Conflicts:
#	knowledge/log.md

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# Conflicts:
#	knowledge/log.md

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# Conflicts:
#	knowledge/log.md

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# Conflicts:
#	knowledge/log.md