core: net/probe + Content-Disposition parser + URL splitter (stage 3)

net/content_disposition — total parser for the mojibake-prone header:
RFC 6266 filename (quoted/token), RFC 5987 filename* ext-values
(charset'lang'pct-encoded, incl. RFC 2231 continuations), legacy RFC 2047
encoded-words (=?UTF-8?B?..?= / ?Q?), and raw Latin-1 bytes; prefers
filename* over filename; strips path components AFTER decoding (a base64
payload can hold '/'). 22-case test table.

net/text_codec (internal) — percent-decode, UTF-8 validation, Latin-1->
UTF-8, base64, RFC 2047 — shared by the CD parser and the URL splitter.

net/url — a small total URL splitter (scheme/userinfo/host/port/path/
query/fragment, http(s) validity) and url_filename() for the last path
segment; used for the filename fallback.

net/probe — HEAD then a ranged GET bytes=0-0 that PROVES resumability
(206 + matching Content-Range + a validator), rather than trusting
Accept-Ranges which servers lie about; the ranged GET is also the HEAD-
refused (403/405/501) fallback. 401/407 -> success result with
requires_auth, not an error. Runs on its own pool (max_concurrent,
default 4) outside the segment budget per ADR 0011 §5. suggest_filename()
does the resolution order (explicit -> disposition -> URL -> download.bin)
with a light strip; rules/ (stage 9) owns the authoritative sanitize.

tools/fuzz — libFuzzer targets for the CD parser and the URL splitter,
compiling the parser sources directly so they're fully instrumented;
self-guards on VELOX_BUILD_FUZZ + Clang (the top-level CMake adds every
tools/* unconditionally). Seed corpora included.

Fixed on the way: a p -> Transfer -> State -> cbs -> p reference cycle in
Prober that leaked every probe (drop the stored Transfer; the worker
keeps State alive). Tests green under ASan/UBSan and TSan.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01HPPSGhiArbvQgwC2DNiURS

core/CMakeLists.txt

@@ -13,6 +13,10 @@ add_library(veloxcore STATIC
     src/util/thread_pool.cpp
     src/net/curl_error.cpp
     src/net/http_client.cpp
+    src/net/text_codec.cpp
+    src/net/content_disposition.cpp
+    src/net/url.cpp
+    src/net/probe.cpp
 )
 add_library(velox::core ALIAS veloxcore)
 
@@ -37,13 +41,7 @@ if(VELOX_BUILD_TESTS)
     add_subdirectory(tests)
 endif()
 
-# libFuzzer is clang-only; a GCC configure with -DVELOX_BUILD_FUZZ=ON (the `ci` preset)
-# must not hard-fail. No fuzz targets exist yet — they arrive with net/probe (stage 3)
-# and meta/veloxpart (stage 5).
-if(VELOX_BUILD_FUZZ AND NOT CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-    message(STATUS "veloxcore: VELOX_BUILD_FUZZ set but compiler is "
-                   "${CMAKE_CXX_COMPILER_ID}; fuzz targets need Clang and will be skipped.")
-endif()
-# When fuzz targets land (stage 3: Content-Disposition, URL; stage 5: .veloxpart.meta),
-# they are added here under `if(VELOX_BUILD_FUZZ AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")`
-# and live in ${CMAKE_SOURCE_DIR}/tools/fuzz (owned by lane CORE).
+# Fuzz targets live in ${CMAKE_SOURCE_DIR}/tools/fuzz (lane CORE) and are wired in by the
+# top-level CMakeLists.txt, which add_subdirectory()s every tools/* with a CMakeLists.
+# tools/fuzz/CMakeLists.txt self-guards on VELOX_BUILD_FUZZ + a Clang compiler.
+# Present: Content-Disposition, URL (stage 3). Coming: .veloxpart.meta (stage 5).