Fix f_518, f_519, f_871, f_1270

[yosuke-wolfssl]

This PR addresses f issues:

• f_518: Correct the mask constant on case 30 to configure foreground color properly
• f_519: Add the guard for findHandle on error path
• f_871: Use GetSkip() in ParseRSAPubKey() and ParseECCPubKey() for bounds check
• f_1270: Fix the length validation

[Copilot]

Pull request overview

This PR addresses several correctness issues across the Windows terminal handling, Windows filesystem porting layer, and internal packet/key parsing code.

Changes:

• Fix Windows console foreground color masking for ANSI attribute case 30 (black foreground).
• Harden Windows WS_FindFirstFileA() by using INVALID_HANDLE_VALUE and guarding output conversion/attribute access on failure.
• Improve public key blob parsing bounds-safety by using GetSkip() in RSA/ECC public key parsing; adjust channel failure length validation.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/wolfterm.c	Corrects the bitmask used when clearing the foreground color bits for attribute 30.
src/port.c	Uses INVALID_HANDLE_VALUE consistently and avoids reading/converting findFileData when FindFirstFileW() fails.
src/internal.c	Uses GetSkip() to bounds-check skipping variable-length fields in RSA/ECC pubkey parsing; updates DoChannelFailure() length check (but currently introduces a parsing-consumption issue).

Comments suppressed due to low confidence (1)

src/internal.c:9409

• After changing the length validation to allow non-zero payloads, this handler still doesn't consume or validate the expected fields of SSH_MSG_CHANNEL_FAILURE. The message payload should include at least the recipient channel ID (uint32), so leaving *idx unchanged will cause DoPacket() to not advance past the payload and corrupt subsequent packet parsing. Please parse/validate the recipient channel ID (and set/advance *idx accordingly), or at minimum advance *idx by len once the payload is accepted (and ideally reject unexpected lengths).

    if (ssh == NULL || buf == NULL || len == 0 || idx == NULL)
        ret = WS_BAD_ARGUMENT;

    if (ret == WS_SUCCESS)
        ret = WS_CHANOPEN_FAILED;

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