Fix strncasecmp bounds and alpha-only case folding

[danielinux]

• Added unit tests for string.c

Ref: fenrir M-4 and L-3

[Copilot]

Pull request overview

Adds a new unit-test target for string.c and adjusts strcasecmp/strncasecmp to avoid non-alphabetic “case folding” while also fixing the strncasecmp iteration bound.

Changes:

• Added unit-string.c with tests covering str(n)casecmp, ctype helpers, memory/string routines, and UART formatting helpers.
• Updated unit-test Makefile to build/run the new unit-string target.
• Updated src/string.c to restrict case-insensitive matching to alphabetic characters and to fix the strncasecmp n bound check.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 8 comments.

File	Description
tools/unit-tests/unit-string.c	Introduces new unit tests for string.c behaviors (including UART formatting helpers).
tools/unit-tests/Makefile	Adds unit-string to the unit-test build and defines how it’s compiled.
src/string.c	Updates strcasecmp/strncasecmp case folding logic and tightens the n stopping condition.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

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