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.

1 files changed, 14 insertions, 0 deletions

diff --git a/docs/PROJECTS.md b/docs/PROJECTS.md
index eae860b..fe6c2a8 100644
--- a/docs/PROJECTS.md
+++ b/docs/PROJECTS.md
@@ -335,6 +335,20 @@ Worth knowing: a correctly-chosen 32-bit ARM database also lets IDA's own
 auto-analysis find Thumb functions — `experiments/fibonacci.bin` yields 54
 functions on load with `arm:ARMv7-A` and none with `arm`.
 
+### Thumb entry points from a vector table
+
+`Shift+T` scans forward from the cursor for **odd pointers** — an ARM function
+pointer carries the mode in bit 0, so a Cortex-M vector table is a list of Thumb
+entry points. IDA won't follow them on a headerless image, because nothing tells
+it those words are pointers at all:
+
+    3 Thumb entries found, 3 disassembled
+
+A word only counts when it is odd, lands inside 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.
+
 ### When analysis finds nothing
 
 Zero functions is what a raw image described wrongly looks like — right file,