fix(session): preserve bitmap source stride

[Marc-André Moreau (mamoreau-devolutions)]

Summary

• Preserve TS_BITMAP_DATA source stride independently of destination bounds for raw, Interleaved RLE, and RDP6 bitmap updates.
• Remove raw 4-byte scanline padding without collapsing padded source columns into following rows.
• Crop only the source extent beyond the destination and reject empty dimensions explicitly; do not add framebuffer bounds suppression.
• Render decoded RDP6 RGB data top-down and retain bottom-up rendering for raw and RLE data.

Why this supersedes the overlapping proposals

• fix(session): Fix bitmap stride mismatch and out-of-bounds writes for xRDP compatibility #1252 identifies both dimensions but applies a clipped stride, which still misaddresses padded source rows; its broad framebuffer-clipping changes are intentionally excluded.
• fix(rdp6): use actual bitmap dimensions instead of rectangle dimensions #1398 correctly identifies the RDP6 stride/orientation issue, but leaves raw and RLE paths unresolved.
• Fix Win7 RDP PDU and bitmap stride handling #1408 includes the related stride issue but also mixes unrelated Win7 activation and web changes; its allocation/inference normalization is unnecessary once source stride is explicit.
• Correctly crop bitmap updates when TS_BITMAP_DATA.width is padded #1436 correctly crops padded rows but repacks each path into temporary buffers; this PR preserves the source stride directly and covers all bitmap codecs.

Specification basis

• MS-RDPBCGR 2.2.9.1.1.3.1.2.2 (TS_BITMAP_DATA): separate destination bounds, dimensions, and bottom-up raw rows with 4-byte row padding.
• MS-RDPBCGR 2.2.9.1.1.3.1.2.3 and 2.2.9.1.1.3.1.2.4: compressed bitmap header and Interleaved RLE stream.
• MS-RDPEGDI 2.2.2.5.1: RDP 6.0 bitmap stream.

Validation

• cargo test -p ironrdp-session --lib
• cargo check -p ironrdp-session --all-features
• cargo clippy -p ironrdp-session --all-targets -- -D warnings
• cargo xtask check fmt -v

[Copilot]

Pull request overview

Preserves bitmap source stride and correct row orientation across raw, RLE, and RDP6 updates.

Changes:

• Separates source stride from cropped destination dimensions.
• Removes raw scanline padding safely.
• Adds stride and orientation regression tests.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
crates/ironrdp-session/src/image.rs	Applies explicit source stride and destination cropping.
crates/ironrdp-session/src/fast_path.rs	Propagates bitmap dimensions and handles padding/orientation.

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[irvingouj@Devolutions (irvingoujAtDevolution)]

LGTM