Release v1.5.1 — update reports the truth, and the session says when you're behind

[r-bart]

Three changes, all found by trying to run devtronic update against this repository.

update announced ~50 files it was never going to write

update walks the template tree twice — once to report, once to apply — and only the apply
loop asked whether the install was in plugin or marketplace mode. Every marketplace user was
shown the whole skill and agent set as "New Files in This Version", confirmed adding them, and
saw none appear. Because the list was never empty, All files are up to date! could not fire
for a marketplace install however current it was.

Both loops now share isPluginManagedPath().

before                          after
Files to Update:  2             Files to Update:  2
New Files:       50             (none)

Migrating to the plugin left the old inline hooks behind

The plugin supplies the same hooks, so both sets ran: the SessionStart prompt fired twice per
session, and the unfiltered npx eslint --fix linted every markdown write alongside the
plugin's filtered auto-lint.sh. Running since the plugin migration, in every migrated
project.

registerGitHubPlugin() now strips them and reports which events it cleaned. Matching is by
signature and deliberately narrow: an unrecognised hook is one the user added, and removing it
takes work they cannot get back. Over half of stripDevtronicHooks()'s tests assert exactly
that.

The session now says when you're behind

A SessionStart hook runs version-check.sh: it compares the version in
.ai-template/manifest.json against the installed CLI and prints one line when they differ,
naming devtronic update or npm i -g devtronic@latest depending on which side is older.

Every part of this has existed since the manifest did. Nothing ran the comparison unless you
typed devtronic info — which is why this repository sat on 1.3.0 through two minor releases
without a word.

Detection only, on purpose. update retires files and asks about the ones you made yours;
applying that unattended is how work gets lost.

Verification

typecheck, lint, build clean. 1120 tests, 53 files.

46 tests cover the three changes, all mutation-checked:

Mutation	Fails
Remove the detection guard	the 50 phantom files return
Treat every hook as devtronic's	the 4 tests protecting the user's hooks
sort -V → sort	numeric version ordering (1.10.0 vs 1.9.0)
Append a byte to the bundled script	the generated/bundled identity check