arm: find Thumb entry points from a vector table (Shift+T)

An ARM function pointer carries the mode in bit 0: odd means Thumb. A Cortex-M
vector table is therefore a list of Thumb entry points, and IDA won't follow them
on a headerless image because nothing tells it those words are pointers at all.
Shift+T scans forward from the cursor and marks them.

  0 functions -> 3 Thumb entries found, 3 disassembled

A word only counts when it is odd, lands in a loaded segment, and its target is
executable and not already data. The even words in a vector table — the initial
stack pointer — fail the first test, which is the point: marking a data word as
code corrupts the listing, so a false positive costs more than a miss. The
fixture includes an even in-range word and an odd OUT-of-range word to keep that
honest.

A note on how this started: I recommended this feature, then probed
experiments/fibonacci.bin for the signal and found ZERO odd in-range pointers —
it's a flat code blob, not a firmware image. Rather than build a detector I
couldn't test, I wrote experiments/cortexm.bin: a real vector table pointing at
small self-contained Thumb handlers. The first version of that fixture aimed its
handlers into the middle of copied code, so two "entries" were really inside one
function — the tool was right and the fixture was wrong, which is worth stating
because I nearly filed it as a bug.

Function creation goes through one _idatui_add_func helper now, shared with
define_func_run: add_func(ea) alone fails on freshly-marked code (IDA can't find
the end), and the scan hit exactly the same wall `p` did.

Status precedence, fixed properly this time. An action's result kept being
overwritten by the reload it triggered — cursor moved, filter re-applied,
functions re-counted. I patched that at FIVE separate call sites before
admitting it's one problem. _status(text, priority=True) now marks a result: it
holds the bar for 8s or until the next keypress, and routine chatter can't
outrank it. The per-site special cases are gone.

tests: +4 thumb (20) — a bare vector table gives IDA nothing, scanning finds
exactly the three handlers, the non-pointer words are ignored, and the result
survives both the reload and the reindex. 209/0 scenarios, 30/0 blob, 30/0
project UI.

5 files changed, 43 insertions, 0 deletions

diff --git a/experiments/cortexm.bin b/experiments/cortexm.bin
new file mode 100644
index 0000000..173bb10
--- /dev/null
+++ b/experiments/cortexm.bin
diff --git a/experiments/fibonacci.bin b/experiments/fibonacci.bin
new file mode 100755
index 0000000..6f7b470
--- /dev/null
+++ b/experiments/fibonacci.bin
diff --git a/experiments/fibonacci.c b/experiments/fibonacci.c
new file mode 100644
index 0000000..26fca0c
--- /dev/null
+++ b/experiments/fibonacci.c
@@ -0,0 +1,43 @@
+#include <stdint.h>
+
+/* Iterative Fibonacci. */
+uint32_t fib_iter(uint32_t n)
+{
+    uint32_t a = 0, b = 1;
+    for (uint32_t i = 0; i < n; i++) {
+        uint32_t t = a + b;
+        a = b;
+        b = t;
+    }
+    return a;
+}
+
+/* Naive recursive Fibonacci. */
+uint32_t fib_rec(uint32_t n)
+{
+    if (n < 2)
+        return n;
+    return fib_rec(n - 1) + fib_rec(n - 2);
+}
+
+/* Memoized Fibonacci (static table). */
+uint32_t fib_memo(uint32_t n)
+{
+    static uint32_t cache[48];
+    if (n < 2)
+        return n;
+    if (n >= sizeof(cache) / sizeof(cache[0]))
+        return fib_iter(n);
+    if (cache[n])
+        return cache[n];
+    return cache[n] = fib_memo(n - 1) + fib_memo(n - 2);
+}
+
+volatile uint32_t sink;
+
+int main(void)
+{
+    for (uint32_t n = 0; n < 20; n++)
+        sink = fib_iter(n) + fib_rec(n) + fib_memo(n);
+    return 0;
+}
diff --git a/experiments/fibonacci.elf b/experiments/fibonacci.elf
new file mode 100755
index 0000000..05ac21d
--- /dev/null
+++ b/experiments/fibonacci.elf
diff --git a/experiments/fibonacci.o b/experiments/fibonacci.o
new file mode 100644
index 0000000..c474d49
--- /dev/null
+++ b/experiments/fibonacci.o