fix(platform): rename linux/posix namespaces to avoid predefined macro conflict

Problem:
- 'linux' is a predefined macro on Linux platforms
- Using 'namespace linux' causes compilation errors
- Preprocessor replaces 'linux' with '1' before compilation

Solution:
- Rename 'namespace linux' to 'namespace linux_'
- Rename 'namespace posix' to 'namespace posix_'
- Update all 7 call sites accordingly:
  - linux/condition.h:  linux_::detail::make_timespec()
  - linux/mutex.h:      linux_::detail::make_timespec() (2 places)
  - posix/condition.h:  posix_::detail::make_timespec()
  - posix/mutex.h:      posix_::detail::make_timespec() (2 places)
  - posix/semaphore_impl.h: posix_::detail::make_timespec()

This prevents preprocessor macro expansion issues while maintaining
the ODR violation fix from the previous commit.

src/libipc/platform/linux/condition.h

@@ -27,7 +27,7 @@ public:
                 return false;
             }
         } else {
-            auto ts = linux::detail::make_timespec(tm);
+            auto ts = linux_::detail::make_timespec(tm);
             int eno = A0_SYSERR(a0_cnd_timedwait(native(), static_cast<a0_mtx_t *>(mtx.native()), {ts}));
             if (eno != 0) {
                 if (eno != ETIMEDOUT) {

src/libipc/platform/linux/get_wait_time.h

@@ -10,7 +10,7 @@
 #include "a0/err_macro.h"
 
 namespace ipc {
-namespace linux {
+namespace linux_ {
 namespace detail {
 
 inline bool calc_wait_time(timespec &ts, std::uint64_t tm /*ms*/) noexcept {
@@ -44,5 +44,5 @@ inline timespec make_timespec(std::uint64_t tm /*ms*/) noexcept(false) {
 }
 
 } // namespace detail
-} // namespace linux
+} // namespace linux_
 } // namespace ipc

src/libipc/platform/linux/mutex.h

@@ -25,7 +25,7 @@ public:
     bool lock(std::uint64_t tm) noexcept {
         if (!valid()) return false;
         for (;;) {
-            auto ts = linux::detail::make_timespec(tm);
+            auto ts = linux_::detail::make_timespec(tm);
             int eno = A0_SYSERR(
                 (tm == invalid_value) ? a0_mtx_lock(native()) 
                                       : a0_mtx_timedlock(native(), {ts}));
@@ -56,7 +56,7 @@ public:
 
     bool try_lock() noexcept(false) {
         if (!valid()) return false;
-        int eno = A0_SYSERR(a0_mtx_timedlock(native(), {linux::detail::make_timespec(0)}));
+        int eno = A0_SYSERR(a0_mtx_timedlock(native(), {linux_::detail::make_timespec(0)}));
         switch (eno) {
         case 0:
             return true;

src/libipc/platform/posix/condition.h

@@ -115,7 +115,7 @@ public:
             }
             break;
         default: {
-                auto ts = posix::detail::make_timespec(tm);
+                auto ts = posix_::detail::make_timespec(tm);
                 int eno;
                 if ((eno = ::pthread_cond_timedwait(cond_, static_cast<pthread_mutex_t *>(mtx.native()), &ts)) != 0) {
                     if (eno != ETIMEDOUT) {

src/libipc/platform/posix/get_wait_time.h

@@ -10,7 +10,7 @@
 #include "libipc/utility/log.h"
 
 namespace ipc {
-namespace posix {
+namespace posix_ {
 namespace detail {
 
 inline bool calc_wait_time(timespec &ts, std::uint64_t tm /*ms*/) noexcept {
@@ -37,5 +37,5 @@ inline timespec make_timespec(std::uint64_t tm /*ms*/) noexcept(false) {
 }
 
 } // namespace detail
-} // namespace posix
+} // namespace posix_
 } // namespace ipc

src/libipc/platform/posix/mutex.h

@@ -196,7 +196,7 @@ public:
     bool lock(std::uint64_t tm) noexcept {
         if (!valid()) return false;
         for (;;) {
-            auto ts = posix::detail::make_timespec(tm);
+            auto ts = posix_::detail::make_timespec(tm);
             int eno = (tm == invalid_value) 
                 ? ::pthread_mutex_lock(mutex_) 
                 : ::pthread_mutex_timedlock(mutex_, &ts);
@@ -230,7 +230,7 @@ public:
 
     bool try_lock() noexcept(false) {
         if (!valid()) return false;
-        auto ts = posix::detail::make_timespec(0);
+        auto ts = posix_::detail::make_timespec(0);
         int eno = ::pthread_mutex_timedlock(mutex_, &ts);
         switch (eno) {
         case 0:

src/libipc/platform/posix/semaphore_impl.h

@@ -88,7 +88,7 @@ public:
                 return false;
             }
         } else {
-            auto ts = posix::detail::make_timespec(tm);
+            auto ts = posix_::detail::make_timespec(tm);
             if (::sem_timedwait(h_, &ts) != 0) {
                 if (errno != ETIMEDOUT) {
                     ipc::error("fail sem_timedwait[%d]: tm = %zd, tv_sec = %ld, tv_nsec = %ld\n",