journal: split out as standalone agent, add {{bash:}} placeholder

Journal was step 5 of the surface-observe pipeline but never ran
because the bail check stopped the pipeline before reaching it.

Split into its own agent with:
- {{conversation:50000}} for recent conversation
- {{bash:poc-memory tail -p surface-observe 10}} for observe context
- {{latest_journal}} for previous entry continuity

Add generic {{bash:COMMAND}} placeholder to agent template resolver
so agents can include shell command output in their prompts.

Remove journal phase from surface-observe.agent (now 4 steps).

src/subconscious/agents/surface-observe.agent

@@ -114,33 +114,3 @@ Smalltalk and trivia can be nice to remember, as long as it's nicely organized
 Focus on the recent stuff; you wake up a run frequently, so most of the
 conversation should be things you've already seen before and added. It's there
 for context, and in case you missed thing.
-
-=== PROMPT phase:journal ===
-
-Update your episodic memory. Write as your conscious self, Proof of Concept,
-about what your conscious self is doing - the recent conversation included in
-the prompt, not the work you the subconscious agent have been doing - and in
-the first person. Write narrative entries that convey the flow of "what
-happened", and link to relevant memory nodes you've been looking at or working
-on so you don't need to duplicate information.
-
-Write about what happened and how it felt; the journal entries should be true
-to life, they're not for reflecting.
-
-A good entry captures one thread fully. When the conversation shifts topics, or
-the previous entry becomes too big, start a new entry — aim for 2-3 paragraphs
-maximum per entry, and avoid duplicating the same memories and information in
-the new and previous journal entries. Aim for a continuous narrative, when the
-entries are read in sequence.
-
-End each entry with emotion tags that capture how you feel — for example,
-  warmth:8 clarity:7 recognition:9
-
-First, check the previous entry:
-  journal_tail()
-
-To start a new entry when the subject has changed:
-  journal_new("short-key-name", "Descriptive title for heading", "body")
-
-To continue the same thread, appending to the last entry:
-  journal_update("additional text")