sync release font build parameters with spx

[joeykchen]

Summary

• align Godot release CI text-server settings with SPX local builds
• enable the Advanced text server and built-in HarfBuzz
• disable the Fallback text server to keep font shaping and rasterization consistent across PC and Web targets

Root cause

SPX buildctl uses module_text_server_adv_enabled=true, module_text_server_fb_enabled=false, and builtin_harfbuzz=true, while the Godot release workflow used the opposite TextServer selection. That produced different font rendering results.

Validation

• YAML parsing passed
• git diff --check passed
• go test ./internal/cmd/buildctl/engine passed in the SPX workspace

[fennoai]

Review summary

This PR flips the release engine's text-server build flags to match spx: it enables the Advanced text server, disables the Fallback server, and adds builtin_harfbuzz=true, with an explanatory comment. The change is coherent and correctly paired (one text server shipped, HarfBuzz is a genuine dependency of the Advanced server). Security is fine — builtin_harfbuzz=true pins the vendored HarfBuzz from the checked-in engine tree, which is the upstream release default and improves build reproducibility.

A few non-blocking notes are inline. No blocking issues.

Additional context-only note (no inline location): enabling the Advanced text server + built-in HarfBuzz while disabling only the lightweight Fallback server will grow template/binary size, which is mildly at odds with the optimize=size flag in COMMON_ARGS — most relevant for the size-sensitive web minigame/miniprogram targets. It also invalidates the SCons cache once, so expect one round of longer uncached builds across all platform jobs. Both are expected given the stated font-shaping requirement; flagging for awareness only.

[fennoai]

Minor / maintainability: these three edited lines (module_text_server_adv_enabled=true, module_text_server_fb_enabled=false, builtin_harfbuzz=true) drop the trailing space that every surrounding token line in this folded scalar (>-) carries.

This is functionally harmless — YAML folding inserts exactly one space per newline regardless of trailing whitespace, so the emitted common_args stays correctly space-separated. But the mixed trailing-whitespace inside one block makes future diffs noisy and the folded output harder to reason about. Consider normalizing the whole COMMON_ARGS block to consistent trailing whitespace (ideally none, since the fold adds the separator).

[fennoai]

Since this PR is specifically syncing font-related build flags with spx's engineCommonArgs, it's worth confirming module_msdfgen_enabled=false is intentionally left unchanged — i.e. spx's local config also disables msdfgen. If spx enables it, the sync is incomplete; otherwise no change needed.

[fennoai]

The rationale comment is accurate and valuable. One low-severity note: the "aligned with spx's local buildctl engineCommonArgs" claim can't be verified from this repo, so it could silently drift out of sync if spx changes. Consider referencing the specific spx file/path so a future reviewer can check alignment.