Get Reef v0.11.1

Added — reef_rt_entropy: one OS entropy hook (RB-016)

• The runtime has one entropy primitive, reef_rt_entropy(buf, len) (reef-runtime/include/reef_entropy.h). Linux and illumos use getrandom(2), the BSDs and macOS arc4random_buf(3), anything else /dev/urandom (also the fallback when the kernel lacks getrandom). It fills every byte or returns a code (1 no source, 2 source failed, 3 bad arguments) with the buffer zeroed. It never falls back to the clock. EINTR from the GC's SIGURG is retried.
• Bare metal: reef_baremetal.c has a weak default that returns "no source". An OS links its own reef_rt_entropy to provide one, as it does reef_putchar.
• Reef code reaches it through sys.platform.runtime.reef_rt_entropy. Prefer the random module, which returns a Result.
• Link test: a strong reef_rt_entropy overrides the weak bare-metal default on amd64 (run and checked by behaviour), aarch64 and riscv64 (checked with nm), with no duplicate-symbol error. If the strong definition is in a static archive linked after reef_baremetal.o, the linker never pulls it in and the weak default is used silently. reef-baremetal/README.md gives the safe link lines (object file, or --whole-archive).

Added — encoding.uuid (RFC 9562) (RB-019)

• v4() and v7(unix_ms) take their random bits from random.random and return a Result (Err(Unsupported) with no entropy source, never a predictable UUID). v7 puts the 48-bit millisecond time first, so UUIDs from different milliseconds sort by time.
• v8(bytes) sets the version and variant bits over the caller's 16 bytes (the caller's array is not changed). v5(namespace, name) is SHA-1 name-based via crypto.sha1, with namespace_dns/url/oid/x500. nil_uuid() and max_uuid() (nil is a reserved word).
• parse accepts only the canonical 8-4-4-4-12 form (either case); format writes lower case. from_bytes / to_bytes use RFC byte order, the order of the ext2/ext4 s_uuid field. Also version, variant, is_nil, is_max, eq, compare.
• Tested against the RFC 9562 Appendix A vectors (v4, v5, v7, v8).
• v4, v8 and to_bytes compile and link for bare metal.

Added — random.random: secure random numbers and a seedable PCG32 (RB-018)

• secure_fill, secure_bytes, secure_u32, secure_u64, secure_below, secure_range (inclusive) and secure_float read the OS source through reef_rt_entropy and return a Result: Err(Unsupported) when the target has no source, Err(IoError) when it fails, Err(InvalidInput) for bad arguments. No silent fallback.
• Pcg32 is a seedable, deterministic generator (PCG-XSH-RR 64/32, bit-identical to pcg-c-basic): pcg32_new(seed, stream), pcg32_from_entropy, pcg32_next_u32/u64, pcg32_below, pcg32_range, pcg32_float, pcg32_bool, pcg32_shuffle. Each generator has its own state, so Active Objects do not share one. Not for secrets.
• Ranges are unbiased (rejection sampling) and floats are in [0, 1).
• Bare metal: reef_baremetal.h has reef_array_length, so modules that call arr.length() (this one, encoding.uuid) compile freestanding.

Changed — math.random: fixes that change seeded sequences (RB-020)

The same seed(n) now gives different random_int_max, random_int_range and random_float results than in 0.11.0. Raw random_int() and random_bool() sequences do not change.

• random_float() could return exactly 1.0 (the divisor was 2^31-1, the largest draw; seed(1584200935) hit it on the first call). It now divides by 2^31, so results are always in [0.0, 1.0).
• random_int_max and random_int_range were biased (random_int() % n favoured small results: for max = 1500000000, values below 647483648 came up 60% of the time instead of 43%). They now use rejection sampling over the full 32-bit draw.
• random_int_range overflowed for spans over 2^31-1: it returned values outside the range, and random_int_range(INT_MIN, INT_MAX) panicked with integer division by zero. Any int span now works.
• seed_time() seeded from the clock in whole seconds, so programs started in the same second got the same sequence. It now seeds from reef_rt_entropy and uses the clock only when the target has no entropy source. math.random is still not for secrets; use random.random.

Fixed — bare-metal reef_panic can be overridden (RB-022)

• The default reef_panic in reef-baremetal/src/reef_baremetal.c was a strong definition, although the README and header comments called it an optional override. A kernel that defined its own reef_panic and linked that file failed with a duplicate symbol (multiple definition in GNU ld, duplicate symbol in ld.lld). It is now weak, like the other hooks. The weak-override link test covers it on amd64 (run and checked by behaviour), aarch64 and riscv64 (checked with nm).

Fixed — math.random links on bare metal (RB-017)

• reef_baremetal defines reef_time (weak, returns 0 = no clock; an OS with an RTC overrides it) and reef_int_to_float (inline). Before, a freestanding image that called math.random.seed_time() or random_float() failed to link with undefined references to both.
• New gate in run_tests.sh: random_link_probe.reef links against reef_baremetal.c on amd64, aarch64 and riscv64, and a strong reef_rt_entropy must override the weak default.