feat(server): adapt gpt5 (#13478)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- New Features
- Added GPT-5 family and made GPT-5/-mini the new defaults for Copilot
scenarios and prompts.

- Bug Fixes
- Improved streaming chunk formats and reasoning/text semantics,
consistent attachment mediaType handling, and more reliable reranking
via log-prob handling.

- Refactor
- Unified maxOutputTokens usage; removed per-call step caps and migrated
several tools to a unified inputSchema shape.

- Chores
- Upgraded AI SDK dependencies and bumped an internal dependency
version.

- Tests
- Updated mocks and tests to reference GPT-5 variants and new stream
formats.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Cargo.lock

@@ -93,7 +93,7 @@ dependencies = [
  "symphonia",
  "thiserror 2.0.12",
  "uuid",
- "windows 0.61.1",
+ "windows 0.61.3",
  "windows-core 0.61.2",
 ]
 
@@ -1691,7 +1691,7 @@ dependencies = [
  "libc",
  "log",
  "rustversion",
- "windows 0.61.1",
+ "windows 0.61.3",
 ]
 
 [[package]]
@@ -2284,7 +2284,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "07033963ba89ebaf1584d767badaa2e8fcec21aedea6b8c0346d487d49c28667"
 dependencies = [
  "cfg-if",
- "windows-targets 0.48.5",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -4732,9 +4732,9 @@ dependencies = [
 
 [[package]]
 name = "tree-sitter"
-version = "0.25.5"
+version = "0.25.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ac5fff5c47490dfdf473b5228039bfacad9d765d9b6939d26bf7cc064c1c7822"
+checksum = "6d7b8994f367f16e6fa14b5aebbcb350de5d7cbea82dc5b00ae997dd71680dd2"
 dependencies = [
  "cc",
  "regex",
@@ -4842,9 +4842,9 @@ dependencies = [
 
 [[package]]
 name = "tree-sitter-scala"
-version = "0.23.4"
+version = "0.24.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "efde5e68b4736e9eac17bfa296c6f104a26bffab363b365eb898c40a63c15d2f"
+checksum = "7516aeb3d1f40ede8e3045b163e86993b3434514dd06c34c0b75e782d9a0b251"
 dependencies = [
  "cc",
  "tree-sitter-language",
@@ -5334,7 +5334,7 @@ version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf221c93e13a30d793f7645a0e7762c55d169dbb0a49671918a2319d289b10bb"
 dependencies = [
- "windows-sys 0.48.0",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -5365,9 +5365,9 @@ dependencies = [
 
 [[package]]
 name = "windows"
-version = "0.61.1"
+version = "0.61.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c5ee8f3d025738cb02bad7868bbb5f8a6327501e870bf51f1b455b0a2454a419"
+checksum = "9babd3a767a4c1aef6900409f85f5d53ce2544ccdfaa86dad48c91782c6d6893"
 dependencies = [
  "windows-collections",
  "windows-core 0.61.2",
@@ -5477,9 +5477,9 @@ dependencies = [
 
 [[package]]
 name = "windows-link"
-version = "0.1.1"
+version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "76840935b766e1b0a05c0066835fb9ec80071d4c09a16f6bd5f7e655e3c14c38"
+checksum = "5e6ad25900d524eaabdbbb96d20b4311e1e7ae1699af4fb28c17ae66c80d798a"
 
 [[package]]
 name = "windows-numerics"