plugin 0.3.0: port search-first rule + 6 new SKILL.md improvements

Promotes the previously session-local search-first write rule into the
canonical plugin and applies items 2-7 from echo-skill-improvements memory:

1. Loading Step 4 and a new mandatory pre-write search section now require
   POST /search/simple/?query=<slug> across all four project lifecycle
   subfolders before creating any slug-addressed note.
2. Daily-note Agent Log uses a resilient PATCH procedure that auto-creates
   the daily note from the template if missing and adds the heading if
   absent before patching.
3. New Style Rule: `created:` is the earliest known date, not "today";
   preserve it on merges.
4. New Project Lifecycle section: incubating / active / on-hold / archived,
   with the rule that folder and frontmatter.status must agree.
5. Session filename pinned to YYYY-MM-DD-HHMM-<slug>.md (lex-sortable);
   existing files left as-is.
6. Loading Step 3: read only the ~5 most recent sessions by reverse lex
   sort instead of the full list.
7. `source_notes` defined as a backward link to inputs; forward links
   belong in `## Related` in the body.

Repo layout: promotes the previously zipped-only plugin to a tracked
source tree at echo-memory.plugin.src/. The .plugin zip is rebuilt
from source on each version bump.

Bumps plugin.json to 0.3.0.

echo-memory.plugin.src/skills/echo-memory/references/session-log-template.md

@@ -0,0 +1,108 @@
+# Session Log Template
+
+Session logs go in: `_agent/sessions/YYYY-MM-DD-HHMM-<slug>.md`
+
+The slug describes what the session was about in 2–5 words, kebab-case.
+Examples: `2026-06-05-1430-echo-plugin-build.md`, `2026-05-14-0900-q1-review-prep.md`.
+
+Keep logs focused. Capture the goal, what was read/done, decisions, outputs, open threads, and the next step. This matches the vault's `_agent/templates/session-log-template.md`.
+
+---
+
+## Template
+
+```markdown
+---
+type: session-log
+status: complete
+created: 2026-06-05T14:30
+updated: 2026-06-05T14:30
+tags: [agent, session]
+agent_written: true
+source_notes: []
+session_date: 2026-06-05
+client: claude-code
+---
+
+# Session Log
+
+## Goal
+One line — what this session set out to do.
+
+## Notes Read
+- [[note]] — why it was relevant
+(omit if none)
+
+## Actions Taken
+Brief narrative or bullets of what was done.
+
+## Decisions Made
+- Decision — why
+(omit section if none)
+
+## Outputs Created
+- `path/or/filename` — what it is
+(omit section if none)
+
+## Open Threads
+- [ ] unresolved question or next step
+(omit section if none)
+
+## Suggested Next Step
+One sentence: what to do first next time on this topic.
+
+## Related
+- [[wikilinks go here, in the body — never in frontmatter]]
+```
+
+---
+
+## Example
+
+```markdown
+---
+type: session-log
+status: complete
+created: 2026-06-05T14:30
+updated: 2026-06-05T14:30
+tags: [agent, session, plugin]
+agent_written: true
+source_notes: ["resources/references/obsidian-local-rest-api.md"]
+session_date: 2026-06-05
+client: claude-code
+---
+
+# Session Log
+
+## Goal
+Build and package the echo-memory CoWork plugin against the live vault.
+
+## Notes Read
+- [[BOOTSTRAP]], [[STRUCTURE]], [[_agent/memory/semantic/operator-preferences]]
+
+## Actions Taken
+Verified the REST API end-to-end, confirmed the scaffold copied into the live vault,
+created missing empty folders, and built the plugin (SKILL + 4 reference files).
+
+## Decisions Made
+- Vault addressed at root — ECHO is a dedicated vault.
+- Key hardcoded in the plugin (not in the vault) — personal plugin, per the reference pattern.
+
+## Outputs Created
+- `echo-memory.plugin` — installable CoWork plugin
+
+## Open Threads
+- [ ] Validate Claude Code direct filesystem access to the vault host.
+
+## Suggested Next Step
+Install the plugin and run a live load/write through it to confirm the skill triggers.
+
+## Related
+- [[projects/active/vault-foundation]]
+- [[resources/references/obsidian-local-rest-api]]
+```
+
+After writing the log, append a one-line entry to the daily note's **Agent Log** section.
+
+> **Reminder:** wiki links go in the body (e.g. this `## Related` section), never in YAML
+> frontmatter. `source_notes` in frontmatter holds plain relative path strings, not `[[links]]`.