Adopt fade_in / fade_out helpers in samples

[Copilot]

The 0.3.1-beta fade_in() / fade_out() helpers (#450) weren't exercised by any sample. Adopt them in the samples called out by the issue, where appropriate.

Sample changes

• slideshow — start at pal_bright(0) and fade_in(4) after ppu_on_all() so the CNROM title fades up.
• scoreboard — swap the static pal_bright(4) for pal_bright(0) + fade_in(4) after ppu_on_all().
• climber — setup_graphics() now ends at pal_bright(0); main flow calls fade_in(4) once the level is drawn and fade_out(4) when the player reaches the top floor. The per-frame hit-flash (pal_bright(vbright) decrementing from 8 → 4) is left alone — it's a flash, not a fade ramp.

Already done, no change

• fade — Phase 1 already uses fade_in(4) / fade_out(4). The bg_fade_in / spr_fade_in helpers ramp pal_bg_bright / pal_spr_bright, for which there is no built-in equivalent, so they stay.
• rletitle — already uses the pal_bright(0) + fade_in(4) pattern.

Example (scoreboard)

pal_col(0, DarkBlue);
pal_col(1, White);
pal_bright(0);          // was: pal_bright(4)
// ...
ppu_on_all();
fade_in(4);             // new

Test data

Rebuilt the three changed samples (Debug + Release), refreshed the embedded src/dotnes.tests/Data/*.{debug,release}.dll, and regenerated the corresponding TranspilerTests.Write.*.verified.bin snapshots.

[Copilot]

Pull request overview

This PR updates several samples to exercise the fade_in(byte delay) / fade_out(byte delay) NESLib helpers (added in #450) by replacing immediate brightness setup with a dark start plus a fade once rendering is enabled, and adding a fade-out at the climber end-of-run transition.

Changes:

• slideshow: Start at pal_bright(0) and call fade_in(4) after ppu_on_all() to fade up the title screen.
• scoreboard: Replace pal_bright(4) with pal_bright(0) + fade_in(4) after ppu_on_all().
• climber: End setup_graphics() at pal_bright(0), fade_in(4) after the stage is drawn, and fade_out(4) when reaching the top floor; test DLLs/snapshots refreshed for the affected samples.

Reviewed changes

Copilot reviewed 3 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
samples/slideshow/Program.cs	Fade in from black after enabling rendering to demonstrate fade_in(4).
samples/scoreboard/Program.cs	Start dark and fade in after ppu_on_all() using fade_in(4).
samples/climber/Program.cs	Start dark in graphics setup; fade in after world draw; fade out on run completion.
src/dotnes.tests/Data/slideshow.debug.dll	Rebuilt test input assembly for updated slideshow sample (Debug).
src/dotnes.tests/Data/slideshow.release.dll	Rebuilt test input assembly for updated slideshow sample (Release).
src/dotnes.tests/Data/scoreboard.debug.dll	Rebuilt test input assembly for updated scoreboard sample (Debug).
src/dotnes.tests/Data/scoreboard.release.dll	Rebuilt test input assembly for updated scoreboard sample (Release).
src/dotnes.tests/Data/climber.debug.dll	Rebuilt test input assembly for updated climber sample (Debug).
src/dotnes.tests/Data/climber.release.dll	Rebuilt test input assembly for updated climber sample (Release).
src/dotnes.tests/TranspilerTests.Write.slideshow.verified.bin	Updated verified ROM snapshot for slideshow due to fade-in behavior change.
src/dotnes.tests/TranspilerTests.Write.scoreboard.verified.bin	Updated verified ROM snapshot for scoreboard due to fade-in behavior change.
src/dotnes.tests/TranspilerTests.Write.climber.verified.bin	Updated verified ROM snapshot for climber due to fade-in/out behavior change.

[jonathanpeppers]

Done — updated to fade_in(4) in f8dc6bb.

[jonathanpeppers]

Done — updated to fade_in(4) in f8dc6bb.

[jonathanpeppers]

Done — updated to fade_in(4) in f8dc6bb.

[jonathanpeppers]

Closing — after review, this PR was adding fade_in / fade_out calls to samples that had no manual fade boilerplate to replace:

• slideshow had no fade at all (PR invented one)
• scoreboard used a static pal_bright(4) (not a ramp)
• climber uses pal_bright(vbright) as a per-frame hit-flash, which Add fade_in / fade_out helpers for palette brightness transitions #450 explicitly called out as "dynamic per-frame game state changes, not simple 0→4 / 4→0 fades"

The only samples with the manual for (vb=0; vb<=4; pal_bright(vb); ppu_wait_frame()) pattern were rletitle and fade, both already migrated in #450. There is no remaining boilerplate to replace, so closing without merging.